Continuously operating filtering apparatus

ABSTRACT

A deep fat fryer with continuous oil filtering and purging of sediments therefrom during uninterrupted fryer operation is provided. The filter includes a cylindrical hollow housing with a first end and a second end and a hollow cylindrical screen with a longitudinal axis and first and second ends. The screen is disposed coaxially within the hollow housing to define an annulus therebetween. A piston mounted within the screen and reciprocatingly movable along the longitudinal axis between the first and second ends of the screen. A pump, seal, and associate motor are provided to provide continuous oil flow through the filter and the remainder of the fryer. A heat exchanger is provided downstream of the pump to transfer heat from the fryer to the oil flowing through the heat exchanger.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of co-pending U.S.application Ser. No. 14/480,160, filed on Sep. 8, 2014 which is adivisional application of U.S. application Ser. No. 12/119,679, filed onMay 13, 2008 and issued as U.S. Pat. No. 8,828,223 on Sep. 9, 2014,which claimed priority under 35 U.S.C. § 119(e) to U.S. ProvisionalApplication No. 60/938,117, filed on May 15, 2007, and to U.S.Provisional Application No. 60/972,972, filed on Sep. 17, 2007, and toU.S. Provisional Application No. 61/050,701, filed on May 6, 2008, theentirety of which are each fully incorporated by reference herein.

TECHNICAL FIELD

Deep fat fryers are known in the restaurant and food service industry asdevices used to cook food products in a pool of heated oil. The heatedoil is normally stored within a vat and the oil is heated from a heatsource provided within the fryer. Fryers may include combustion heatsources that generate heat by burning natural gas or other types of fuelin the presence of a source of air, and direct the heated air toexchange heat with (either directly or indirectly) the oil within thevat. Fryers may also generate heat with electric heaters that generatesignificant amounts of heat and are in either direct or indirect contactwith the vat of oil within the fryer. Deep fat fryers are frequentlyused to prepare many types of food products, such as potatoes, chicken,and fish. Deep fat fryers are frequently used for preparing these typesof food due to the agreeable taste and the speed and efficiency ofpreparation of the food products.

The external surfaces of food products may be covered with breadcrumbs,flour, or similar substances prior to being placed within vat of oil toprovide a pleasing exterior surface of the food after cooking within theoil. During the cooking process, some of the breadcrumbs, or similarsubstances, become separated from the food products and are eventuallyentrained within the oil. Other food products, such as potatoes, are notgenerally covered with breadcrumbs or the like, but often have some ofthe external surface of the potato fall from the item and into the oilduring the frying process. The amount of foreign particulate matterwithin the oil increases as the fryer is used and hastens thedegradation of the oil used in the frying process, degrades the tasteand appearance of the food cooked within the fryer, and can reduce thecooking efficiency of the fryer. Accordingly, for longevity of thecooking oil, satisfactory tasting food, and efficient cooking, the oilwithin the vat of the fryer must be filtered or otherwise cleanedfrequently.

In most conventional fryers, the oil must be at least partially orcompletely drained from the vat into a separate filtering assembly tofilter the oil. The oil is generally filtered by passing the oil throughfilter media, typically a paper, cloth, metal, or nylon screen or meshthat mechanically removes the foreign particulate matter entrainedwithin the oil that cannot fit through the mesh. All of the oil from thefat is passed through the mesh at least once, and the particulate matteris removed from the mesh and discarded. The resultant oil has asignificantly lower particulate matter content and then can be pumpedback to the fryer vat for further cooking.

This conventional filtering process is a relatively inefficient becausethe fryer cannot be operated while the oil is filtered because it mustbe drained from the vat and transferred to the filter apparatus.Further, while the oil is drained and filtered, no heat is being addedto the oil and the oil temperature accordingly decreases, and must bethen heated up to nominal operational temperature prior to use. Thiscooling and subsequent heat up of the oil requires more energy thanwould be required to maintain the oil of an idling fryer at the nominaluse temperature. Such systems require significant labor to maintain thefilter in an acceptable operating state, often requiring the steps ofcleaning the filter apparatus and replace the filter media. Accordingly,because of the periodic filtering requirements many restaurants or foodservice establishments filter the oil from their fryers at least dailyduring a period of low use or often when the establishment is not openfor business. This filtering schedule requires additional staff to bepresent at the establishment when not open for business, which increasesthe labor costs. Also, filtering is often a relatively complicatedprocess (or one with problematic or catastrophic results if performedimproperly) such that only trained employees can effectively and safelyperform this task.

Over time there have been attempts at developing systems for filteringoil coincident with the cooking process. Previous designs that haveincluded continuous oil filtering structures have been disclosed in theprior art, and all include drawbacks that have limited their commercialsuccess. In a design disclosed in U.S. Pat. No. 4,623,544, a filter isprovided in fluid communication with a pump and a heat exchanger toreceive oil flow downstream of the pump and the heat exchanger. Thefilter receives only a portion of the oil flowing through the pump,which lengthens the time to filter the entire oil volume of the fryer.In addition, the unfiltered oil passing through the heat exchanger canresult in clogging of the heat exchange passages preventing proper flow.The filter must be periodically manually cleaned by the operator toavoid reduction in flow though the filter due clogging by foreignmaterial. Further, problems with the design of the disclosed pumpassociated with the filter were noted during continued operation due tothe heat buildup within the pump after continuously operating to pumpheated oil therethrough. It is known in the art that pump seals have avery short useful life if operating at a temperature close to thenominal fryer oil temperature, such as between 325 and 350 degreesFahrenheit. Seals degrade with operation at these high temperatures,which allows oil leakage resulting in loss of cooking oil that mayprevent continued use of the equipment. Over time, oil leakage can alsocause structural deformity that accelerates the failure of other pump ormotor components. Prior art designs often used centrifugal pumps thatwere prone to cavitation and interruption of flow created by steamcaptured within the cooking oil and a resulting decrease of net positivesuction head at the pump suction.

U.S. Pat. No. 4,599,990 discloses a second fryer design that allows forcontinuous filtering of oil within a fryer. In this design a filter isdisposed below the tank and receives a portion of oil that is pumpedthrough a pump with the other portion of the oil pumped by the pumpflowing through a heat exchanger within the fryer. The filter must bemanually cleaned periodically to allow proper flow through the filterand therefore the entire fryer oil circulation system.

U.S. Pat. No. 4,487,691 provides a disclosure of a similar fryer as the'990 patent discussed above. The '691 patent discloses additionalstructural details of the filter system associated with the fryer. Thefilter receives only small fraction of the oil flowing through the pump(e.g. about 10 percent by volume with the remaining oil flowing througha heat exchanger in parallel) so the filter system must be operated forextended periods of time until all of the oil within the fryer becomesfiltered, which prevents the oil from being maintained in asubstantially clean condition and accelerates the end of life of theoil. Additionally, the filter must be manually removed to be cleanedwith requires a relatively complicated and time consuming process.Further, the filter can only be cleaned with the fryer secured, whichreduces the time that the fryer can be used to cook food product. It isdesired to provide a fryer that can continuously filter oil, where thefilter can operate continuously without operator action or cleaning andthe filter cleans large volumes of oil within the fryer within a shorttime, to maintain the oil in a clean and substantially foreign substancefree condition.

BRIEF SUMMARY

A first representative embodiment of the disclosure provides acontinuous filter for a deep fat fryer. The filter includes acylindrical hollow housing with a first end and a second end and ahollow cylindrical screen with a longitudinal axis and first and secondends disposed coaxially within the hollow housing to define an annulustherebetween. A piston is mounted within a passage defined by the screenand movable along the longitudinal axis between the first and secondends of the screen.

A second representative embodiment of the disclosure provides a filterfor a deep fat fryer. The filter includes a hollow cylindrical housingwith an inlet and an outlet and a cylindrical screen coaxially disposedwithin the housing, the screen comprising an inlet in communication withthe housing outlet, and a plurality of holes defined in the screen. Apiston is reciprocatingly translatable along a longitudinal axis of thescreen.

A third representative embodiment of the disclosure provides an oil pumpfluidly connected with a cooking appliance. The oil pump includes amotor with a motor shaft projecting therefrom and a pump within a pumphousing. The pump receives torque from the motor shaft causing the oilpump to rotate through a transmission. A seal is disposed between themotor and the oil pump and adapted to substantially prevent oil leakagefrom the oil pump, wherein the seal is disposed linearly away from thepump housing.

A fourth representative embodiment of the disclosure provides a deep fatfryer. The fryer includes a vat to receive a quantity of cooking oil, afilter to receive oil from the vat and an extraction mechanism toautomatically and cyclically remove debris contained within the filter.A pump continuously operates during operation of the fryer to receivesubstantially the entire volume of oil flowing through the filter. Alength of piping is provided downstream of the pump and positioned toreceive heat from a heat source and a plurality of apertures aredisposed downstream of the piping to allow oil from the piping into thevat.

A fifth representative embodiment of the disclosure provides a methodfor continuously filtering oil in a cooking appliance. The methodincludes the steps of receiving a continuous source of cooking liquidfrom a liquid receptacle in the cooking appliance within a housing andfiltering the cooking liquid through a hollow screen concentricallydisposed within the housing to define an annular space therebetween. Apiston positioned with a passage defined by the screen is cyclicallytranslatably movable between the first and second ends of the screen toremove particulate matter retained on an inner portion of the screen.The method further includes the steps of automatically controlling thetranslation of the piston by a control system based on at least oneoperational parameter of the cooking appliance and continuously pumpingfiltered liquid from the annular space.

A sixth representative embodiment of the disclosure provides a methodfor urging oil flow through a deep fat fryer. The method includes thesteps of providing a motor with a motor shaft projecting therefrom andproviding an oil pump within a pump housing. The oil pump receivestorque from the motor shaft, causing the oil pump to rotate. The methodadditionally includes the step of providing a seal disposed between themotor and the oil pump and adapted to substantially prevent oil leakagefrom the oil pump, wherein the seal is spaced away from the pumphousing.

A seventh representative embodiment of the disclosure provides a methodof constructing a deep fat fryer. The method includes the steps ofproviding a vat to receive a quantity of cooking oil and providing afilter to receive oil from the vat. The method further includes thesteps of providing a pump arranged to continuously operate duringoperation of the fryer to receive oil from the filter, providing alength of piping downstream of the pump and positioned to receive heatfrom a heat source, and providing a plurality of apertures downstream ofthe piping to allow oil from the piping into the vat.

An eighth representative embodiment of the disclosure provides a cookingliquid circulation system for a cooking appliance. The system includes ahousing that is configured to receive a volume of liquid for cooking afood product within a vat and a pump. A primary screen is configured toselectively receive liquid from the vat and allow liquid communicationwith the pump. A second filter assembly is provided that includes ahousing forming a first liquid flow path therethrough to provide liquidcommunication between the vat and the primary filter. A second screen isdisposed coaxially around the first liquid flow path, and an outlet isprovided in selective fluid communication between the first liquid flowpath and the pump through the second screen in a first direction.

A ninth representative embodiment of the disclosure provides a liquidcirculation system for a cooking appliance. The system includes ahousing configured to continuously receive a volume of liquid forcooking a food product within a vat, a pump, and a primary filterconfigured to selectively receive liquid from the vat and allow liquidcommunication with the pump while substantially preventing anyparticulate matter entrained with the volume of liquid from flowing tothe pump with the liquid. A second filter assembly comprising a housingforms a first liquid flow path therethrough to provide liquidcommunication between the vat and the primary filter, a second screen isdisposed coaxially around the first liquid flow path, and an outletprovided in selective fluid communication between the first liquid flowpath and the pump through the second screen in a first direction.

A tenth representative embodiment of the disclosure provides acontinuous filter system for a cooking appliance. The system includes acylindrical primary housing and a cylindrical primary screen disposedconcentrically therein. A flow path is configured for continuous flow ofa liquid to be filtered from a cooking appliance, wherein the pathextends into an internal volume defined by the primary screen. Theprimary screen is configured to allow liquid through the primary screeninto an annulus defined between the housing and the primary screen, butsubstantially retain any particulate matter initially entrained in theliquid within the internal volume. A pump is provided that includes asuction fluidly connected to the annulus and a discharge fluidlyconnected to a return in the cooking appliance. The primary housing isfluidly connected to a debris extraction mechanism to continuouslyreceive the particulate matter therefrom and automatically remove theparticulate matter from the filter system.

An eleventh representative embodiment of the disclosure provides amethod of removing particulate matter from a liquid in a cookingappliance. The method includes the steps of receiving liquid withparticulate matter from a retention volume within the cooking applianceand filtering the liquid with a cylindrical screen disposed within aprimary filter. The method further includes the steps of automaticallyscraping particulate matter from an inner surface of the primary screenand receiving scraped particulate matter within a debris extractionmechanism. The method further includes the steps of compressing theparticulate matter within the debris extraction mechanism andautomatically removing the particulate matter from the debris extractionmechanism.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of the continuously filtering fryer with aportion of the housing removed.

FIG. 2 is a side view of the fryer of FIG. 1, showing the air and oilflow paths through the fryer.

FIG. 2a is the side view of the fryer of FIG. 1, with a plurality ofelectrical resistance heaters provided therein.

FIG. 3 is a perspective view of the heat exchanger of FIG. 1.

FIG. 4 is a perspective view of the continuous filter of FIG. 1.

FIG. 5 is a perspective view of a portion of the filter of FIG. 4 withthe motor and transmission removed.

FIG. 6a is a cross-sectional view of the filter of FIG. 4 with thepiston in a first operation position.

FIG. 6b is the view of FIG. 6a with the piston and end cap in a firstremoval position.

FIG. 7a is the view of the FIG. 6a with the piston in a secondoperational position.

FIG. 7b is the view of FIG. 6a with the piston in a second removalposition.

FIG. 8 is a perspective view of the housing of the filter of FIG. 4.

FIG. 9 is a perspective view of the screen of the filter of FIG. 4.

FIG. 10 is a perspective view of the piston of the filter of FIG. 4.

FIG. 11 is a perspective view of the collar of the filter of FIG. 4.

FIG. 12 is a perspective view of the motor and oil pump of the fryer ofFIG. 1.

FIG. 13 is the view of FIG. 12 showing a recirculation line for the oilpump.

FIG. 14 is an exploded view of the motor and oil pump of FIG. 12.

FIG. 15 is an exploded view of the seal assembly of the motor and oilpump of FIG. 12.

FIG. 16 is a perspective view of the seal assembly of FIG. 12.

FIG. 17 is a side view of an alternate filter of the fryer of FIG. 1.

FIG. 18a is a cross-sectional view of the filter of FIG. 17 showing thepiston in an operating position.

FIG. 18b is the view of FIG. 18a showing the piston in a removalposition.

FIG. 19 is a perspective view of the piston of the filter of FIG. 17.

FIG. 20 is a schematic of the input signals to and the output signalsfrom the control system of the fryer of FIG. 1.

FIG. 20a is a schematic view of another control system.

FIG. 20b is a schematic view of another control system.

FIG. 21 is a perspective view of an alternate filter of the fryer ofFIG. 1.

FIG. 22 is a cross-sectional view of the filter of FIG. 21.

FIG. 23 is another cross-sectional view of the filter of FIG. 21 with aportion of the components therein removed.

FIGS. 24a-24d are portions of an exemplary logic diagram for theoperation of the control system of the filter for the fryer of FIG. 1.

FIGS. 25a and 25b are exemplary logic diagrams for control the oil pumpand threaded rod of the fryer of FIG. 1.

FIG. 26 is an exemplary logic diagram for the starting position circuitof the control system of FIGS. 24a -24 d.

FIG. 27 is a side view of an alternate fryer with a continuous filtersystem.

FIG. 28 is a schematic view of the oil flowpath through the fryer ofFIG. 27.

FIG. 29 is a cross-sectional view of a secondary filter assembly of thefryer of FIG. 27.

FIG. 29a is a detail view of FIG. 29.

FIG. 30 is a perspective view of a primary filter of the fryer of FIG.27 with the piston in a home position.

FIG. 31 is the view of 30 with the piston at the operational end of thehousing.

FIG. 32 is the view of FIG. 30 with the end cap withdrawn and the legrotated to contact the piston.

FIG. 33 is a perspective view of an alternate piston and lineartransmission of the fryer of FIG. 27.

FIG. 34a is a front perspective view of the piston of FIG. 33.

FIG. 34b is a rear perspective view of the piston of FIG. 33.

FIG. 35 is a cross-sectional view of the primary filter oriented asshown in FIG. 32.

FIG. 35a is a detail view of FIG. 35.

FIG. 36 is a perspective view of a primary screen of the primary filterof FIG. 30.

FIG. 37 is a perspective view of a secondary screen of the fryer of FIG.27.

FIG. 38 is a perspective view of another filter mechanism.

FIG. 39 is an exploded view of the filter mechanism of FIG. 38.

FIG. 40 is a perspective view of the debris extraction mechanism in anormal position of the filter mechanism of FIG. 38.

FIG. 41 is a top view of the debris extraction mechanism of FIG. 40.

FIG. 42 is a bottom perspective view of the debris extraction mechanismof FIG. 40.

FIG. 43 is the debris extraction mechanism of FIG. 40 in an extractionposition.

FIG. 44 is another perspective view of the debris extraction mechanismof FIG. 43.

FIG. 45 is an exploded view of a portion of the filter mechanism of FIG.38.

FIG. 46 is a perspective view of an assembly of the filter mechanism ofFIG. 38 configured to connect with three cooking appliances in parallel.

FIG. 47 is a perspective view of a fryer fluidly connected to a remoteoil storage tank.

FIG. 48 is a side schematic view of the filter mechanism of FIG. 38.

FIG. 49 is a schematic line drawing of the filter mechanism of FIG. 38.

FIG. 50 is a perspective view of the filter mechanism of FIG. 38 with achopping mechanism in the retracted position.

FIG. 51 is the view of FIG. 50 with the chopping mechanism in a lowerposition.

FIG. 52 is a perspective view of a portion of the chopping mechanism ofFIG. 50.

DETAILED DESCRIPTION

Turning now to FIGS. 1-2, a cooking appliance is provided. The cookingappliance may be a deep fat fryer 10, or another type of cookingappliance, such as a pasta cooker or rethermalizer, where a food productis cooked in a volume of heated liquid. One of ordinary skill in the artwill recognize that the disclosure herein can be used successfully onother machines where there is a need to continuously remove particulatematter from a volume of liquid therein and/or provide heat to the liquidafter removing particulate matter from the liquid.

The fryer 10 includes a housing 12 that mechanically supports all of thecomponents of the fryer. The fryer 10 includes a vat 14 that provides aopen volume for storing and heating a quantity of cooking oil for fryinga food product placed therein. The fryer 10 further includes a heatsource (not shown) that provides heat to the cooking oil stored withinthe open vat 14. The heat source may be a provided by burning naturalgas or similar fuel in an open flame that heats air passing through thefryer 10, or alternatively, the heat source may be provided by aplurality of electrical heaters that are disposed in the proximity ofthe heat exchanger (discussed below) or another portion of the fryer 10where heat from the heaters may be transferred to the oil of the fryer10.

The fryer 10 includes a filter 20 and an oil circulation system 110 thatallows oil to flow from the vat 14 through the filter 20, through a heatexchanger 130, and return to the vat 14. Oil flow through the oilcirculation system 110 is urged with a pump 121 that may be disposedbetween the filter 20 and the heat exchanger 130. In this embodiment,the pump 120 draws a suction from the outlet of the filter 20, whichurges oil flow through the screen 40 of the filter 20, as discussedbelow. Oil initially gravity drains from the vat 14 to the filter 20,which is disposed below the vat 14 and connected to the vat 14 with alength of piping. The oil discharges from the pump 120 at an increasedpressure, causing flow through the heat exchanger 130 and then through aring 140 connected downstream of the heat exchanger 130. Heated oilflows through a plurality of apertures 142 in the ring 140 to return tothe vat 14.

All oil flowing through the pump 120 and the heat exchanger 130additionally flows through the filter 20, which shortens the time tofilter all oil within the fryer, increases the amount of oil filteringcycles that occur during a fixed operational time of the fryer, whichallows the oil to be maintained in a cleaner state (i.e. less foreignmatter entrained within the oil) and contributes to a longer useful lifefor the oil.

Turning now to FIGS. 4-11, the filter 20 includes a hollow cylindricalhousing 30 that supports and encloses a screen 40. A piston 50 istranslatably mounted within the screen 40. End cups 70 are disposed oneach end of the housing 30 and are longitudinally movable when urged bythe piston 50. The housing 30 includes an outlet slot 36 c on the endsthereof that allows foreign particulate matter 600 that is preventedfrom flowing through the screen 40 to exit the filter 20 for disposal.The housing 30 may be disposed above a filter pan (not shown) or othersuitable structure to provide for a temporary storage location for theforeign particulate matter 600 removed from the oil.

As best shown in FIG. 8, the housing 30 includes a first end 31 and asecond end 32 and a longitudinal axis 30 a therebetween. The housing 30further includes an inlet aperture 33 a and one or more outlet apertures33 b. One or more of the outlet apertures 33 b may be on the oppositeside of the housing 33 from the inlet aperture 33 a to allow for gravityflow of oil from the housing 33, and one or more of the outlet apertures33 b further may be disposed on the top surface of the housing 33 (inthe vicinity of the inlet aperture 33 a) to allow any gas that may havebeen entrained in the oil to be vented from the housing 30 beforeentering the oil pump 120. The first and second ends 31, 32 of thehousing 30 may be open and each may fixedly receive a respective firstand second collar 36, discussed below.

As best shown in FIGS. 6a-7b and 9, a screen 40 is disposed within thehollow internal volume of the housing 30 and situated coaxially withinthe housing 30. The screen 40 is substantially cylindrical and includesa first end 41 that corresponds with the first end 31 of the housing 30and a second end 42 that corresponds with the second end 32 of thehousing 30. The screen 40 includes an outer diameter that is slightlysmaller than the inner diameter of the housing 30 to form an annulus 39between the two. In some embodiments, the annulus 39 may be about 0.125inches wide around the circumference and the length of the screen 40,which provides adequate volume for oil that flows through the pluralityof holes 46 (discussed below) of the screen to flow to the outlet 33 bof the housing 30, while minimizing the size of the housing 30. In otherembodiments, the annulus 39 (and other components of the filter 20) maybe formed with geometries and sizes that are appropriate for thequantity of oil to be continuously filtered.

The screen 40 includes an inlet aperture 43 that is disposed in fluidcommunication with the inlet aperture 33 a of the housing 30. The screen40 is fixed to the housing 30 to prevent relative motion between the twomembers. The screen 40 is formed with a plurality of holes 46 definedthrough the thickness of the screen 40 and provided throughout thesurface of the entire screen 40. In some embodiments, the plurality ofholes 46 may be uniformly spaced throughout the surface area of thescreen 40, while in other embodiments, the plurality of holes 46 may bedisposed in predetermined arrangements. In some embodiments, theplurality of holes 46 may be disposed between about every 0.003 inchesand about every 0.020 inches along the length of the screen. In someembodiments, the distance between the plurality of holes 46 isapproximately the same as the outer diameter of the holes as discussedbelow. In other embodiments, the holes 46 may be a larger distance apartthan the diameter of the plurality of holes 46. In a representativeembodiment, the plurality of holes 46 may be approximately 0.015 inchesapart.

The plurality of holes 46 are defined to allow oil to pass from theinternal volume 44 of the screen 40 to the annulus 39 defined betweenthe housing 30 and the screen 40, while substantially preventing foreignmaterials (such as dirt, crumbs, etc.) entrained with the oil to flowthrough the plurality of holes 46. In some embodiments, the minimumdiameter of the plurality of holes 46 may be between about 0.003 inchesto about 0.017 inches. In some embodiments, the minimum diameter of theplurality of holes 46 may be one of 0.003 inches, 0.005 inches, 0.007inches, 0.009 inches, 0.011 inches, 0.013 inches, 0.015 inches, oranother suitable diameter. This range of potential minimum diameters ofthe plurality of holes 46 is selected to prevent a significant amount offoreign material entrained within the oil from flowing through theplurality of holes 46 such that the oil entering the annulus 39 issubstantially free of foreign materials. Additionally, substantially allforeign materials entrained within the oil entering the filter 20 isretained within the internal volume of the screen 40.

The cross-section of the plurality of holes 46 may be cylindricallyshaped (i.e. with a constant diameter along the length of the hole 46)or in other embodiments, the plurality of holes 46 may be shaped as atruncated cone. In embodiments with conical holes 46, the minimumdiameter of each of the plurality of holes 46 is at the inner surface ofthe screen 40, while the larger diameter of each hole 46 is at the outersurface of the screen 40, which promotes the ability of the piston 50 toclean the screen 40. The plurality of holes 46 may be defined in thescreen 40 with a laser or chemical etching process, or with othermanufacturing processes that are known in the art.

After the oil passes through the plurality of holes 46 and into theannulus 39, the foreign material previously entrained with the oil mayadhere to the internal surface of the screen 40, or the foreign materialmay fall to the bottom internal surface of the screen 40 due to gravity.After extended operation of the filter 20, a significant quantity offoreign material will collect within the internal volume of the screen40, with a minimum amount of oil entrained therein. With extendedoperation, the build-up of foreign material adhering to the screen 40blocks an increasing number of holes 46, which increases pressure dropthrough the filter 20.

As best shown in FIGS. 6a-7b and 10, the filter 20 additionally includesa disc-like piston 50 longitudinally and reciprocatingly mounted withinthe inner volume 40 a of the screen 40. The piston 50 may be circular tocorrespond to the circumference of the screen 40. In other embodiments(not shown) where the screen 40 is a different shape, the piston 50 isformed with a similar, but slightly smaller, shape. The piston 50includes one or more rings 52 that are received within a slot in theouter circumference of the piston 50. The outer diameter of the ring 52when compressed into the slot in the piston 50 is substantially the sameas the inner diameter of the screen 40, such that the ring 52 scrapesagainst the inner surface of the screen 40 as the piston 50 translateswithin the screen 40.

In other embodiments, the piston 50 may include a plurality of sidesurfaces that are extendably mounted to the piston 50 and biasedradially outward by an internal spring. The side surfaces are configuredto scrape along the internal surface of the screen 40 to removeparticulate matter 600 from the screen 40 as they are biased outward tocontact the internal surface of the screen 40.

The piston 50 further includes a threaded central aperture 55 disposedcoaxially with the center of the piston 50 and a second aperture 56disposed on the piston 50 at a radial location from the central aperture55. The central aperture 55 receives a threaded rod 62 therethrough thatextends between the first and second ends 31, 32 of the housing 30. Afirst end 62 a of the threaded rod 62 is rotatably connected to atransmission 63 that receives torque from a motor 64 to selectivelyrotate the threaded rod 62. The second end 62 b of the threaded rod 62extends through a central aperture 71 in the second end cup 70, whichconstrains the translation of the second end cup 70. The threaded rod 62additionally extends through a central aperture 71 in the first cup 70,which is disposed on the first end 41 of the screen 40.

The piston 50 includes opposing side surfaces 53, 54 that may be planaror alternatively, the side surfaces may be formed with a concave profileor a convex profile, as shown in the figures. Further, the side surfaces53, 54 may be formed as a truncated cone with a central planar portionand a conical outer portion. The side surfaces 53, 54 of the piston 50may be formed with the same or differing profiles. The inner surface 73of the end cup 70 that contacts the piston 50 when the piston 50 may beformed as a planar surface, or a complementary or opposing shape to theshape of the side surfaces 53, 54 of the piston 50.

In some embodiments, the motor 64 that ultimately causes the threadedrod 62 to rotate may be the same as the motor 150 that drives the pump120. In other embodiments, the motor 64 driving the threaded rod mayseparate from the motor 150 that drives the pump 120. In embodimentswhere the same motor drives both the pump 120 and the threaded rod 62, aclutch (not shown), is provided between either the motor 64 and thetransmission 63, or alternatively, between the transmission 63 and thethreaded rod 62 to selectively allow rotation of the threaded rod 62(with instruction from the control system 90, discussed below) becausethe motor is constantly operating to drive the pump 120 for continuousoil flow through the filter 20 and the heat exchanger 130. The threadedrod 62 is rotatable in both rotational directions to cause the piston 50to translate in both longitudinal directions within the internal volumeof the screen 40.

A second rod 68 is disposed within the internal volume of the screen 40in parallel with the longitudinal axis 30 a of the housing 30 and thethreaded rod 62. The second rod 68 extends through the second aperture56 of the piston 50 and respective second apertures 72 of the first andsecond end cups 70. The second rod 68 prevents the piston 50 fromrotating with the rotation of the threaded rod 62, such that the piston50 moves linearly along the screen 40 as the threaded rod 62 rotates.

As best shown in FIGS. 6a-7b , the first and second end cups 70 aredisposed at respective first and second ends 31, 32 of the housing 30.Specifically, the first and second end cups 70 are translatably disposedwithin a portion of the respective end of the screen 40 and a portion ofthe respective first and second collars 36. Both of the first and secondend cups 70 are constructed in the same manner and for the sake ofbrevity, a single one of the first and second end cups 70 will bediscussed here. The end cup 70 is a generally cylindrical member with aninner surface 73 and an outer surface 74. The first end cup 70 isdisposed within the housing 30 such that the inner surface 73 faces thepiston 50 within the screen 40 and the outer surface 74 is visible fromoutside an end of the filter 20. The end cups 70 are normally disposedsuch that the outer surface 74 of the end cup 70 is substantially planarwith an outer edge 36 b of the collar 36.

The end cup 70 includes a central aperture 71 that receives the threadedrod 62 therethrough and a second aperture 72 that receives the secondrod 68 therethrough (FIG. 5). A plurality of seals (not shown), such aso-rings and lip seals, may be provided with the central aperture 71 andthe second aperture 72 to prevent oil leakage through the end cup 70from the internal volume 44 of the screen 40.

Each of the first and second collars 36 are substantially hollowcylindrical members and are disposed on a respective first or second end31, 32 of the housing 30. Because each of the first and second collars36 operate and are constructed in the same manner, for the sake ofbrevity the first and second collars 36 are discussed together. Thecollar 36 may include a flanged portion 36 a with an inner diameterslightly larger than the outer diameter of the housing 30, such that theflanged portion 36 a is assembled around the outer surface of therespective first or second end 31, 32 of the housing 30. Each collar 36includes a slot 36 c that provides for fluid communication radially fromthe internal volume of the collar 36 (and the housing 30) to outside thefilter 20. The collar 36 includes an outer edge 36 b (FIG. 11) thatprovides a normal restraining surface for a retaining plate 79.

First and second end cups 70 are biased toward the opposite end cup 70by a spring or similar biasing member 78. The end cup 70 is biasedinward within the housing 30 (i.e. toward the opposing end cup 70 on theopposite end of the housing 30) until the end cup 70 is substantiallyproximate to the respective end of the screen 40. In some embodiments, abiasing member 78 is operatively engaged with both first and second endcups 70 to bias each end cup 70 toward the opposing end cup 70. In otherembodiments, a dedicated biasing member 78 for each end cup 70 may beprovided, with an end connected to the housing 30 or another suitablesurface and the opposite end operatively connected with the end cup 70.

As shown in FIG. 5, a retaining plate 79 may be disposed on the outeredge 36 b of each collar 36 that provides a fixation member for each ofthe opposite sides of the biasing member 78. Accordingly, in use(discussed below) when one of the end cups 70 is translated away fromthe opposing end cup 70 by the piston 50, the retaining plate 79 ispushed outward away from the outer edge 36 b of the collar 36 and thebiasing member 78 is stretched. As the pressing force against the endcup 70 is removed, the biasing member 78 urges the end cup 70 back toits normal position until a seal mechanism 75 (FIGS. 6a-7b ) sealssealing the end cup 70 to the collar 36 to minimize the oil leakage fromthe ends of the housing 30. The seal may be an elastomeric or a metallicseal.

As shown schematically in FIG. 20, a control system 90 is provided tocontrol the motion of the piston 50 within the internal volume of thescreen 40. The control system 90 receives inputs that relate theposition of the piston 50 within the housing 30 and other inputs thatrelate to the operational performance of the screen 40. Specifically, insome embodiments, the control system 90 receives a signal that isproportional to the number of rotations of the threaded rod 62, whichwith the knowledge of the initial position of the piston 50 within thescreen 40 and the dimensions of the threads of the threaded rod 62 andthe length of the filter 20 components, allows the control system 90 todetermine the actual location of the piston 50 within the screen 40.

Alternatively, a one or more limit switches (not shown) or otherpositioning detection structures may be provided within the housing.Specifically, limit switches may be mounted to be directly or indirectlycontacted by the piston 50, or in other embodiments limit switches maybe mounted to be directly contacted by the end cups 70. In oneembodiment, two limit switches may be provided on each end 31, 32 of thehousing 30 in proximity to the end cups 70. A first limit switch may bepositioned to be contacted by the end cup 70 when the end cup 70 is inits normal position with the outer surface 72 planar with the outer edge36 b of the collar. A second limit switch that is operated when the endcup 70 is extended outward from the center of the housing 30 and theinner surface 71 of the end cup 70 is beyond or in-line with the slot 36c in the collar 36, to allow the particulate matter 600 collectedbetween the piston 50 and the end cup 70 to be forced, or gravitydrained through the slot 36 c in the collar 36 and exit the filter 20.

In addition to the information relating to the position of the piston 50within the screen 40, the control system 90 receives data relating tothe operational status of the filter 20. In one embodiment, the controlsystem 90 receives signals that are proportional or representative ofthe pressure at the inlet aperture 33 a of the housing 30 and a secondsignal that is proportional or representative of the pressure at theoutlet aperture 33 b of the housing 30. The differential pressure acrossthe housing 30 is an indication of the relative ease of oil flow throughthe screen 40, the higher the differential pressure, the morerestriction or resistance to oil flow through the filter 20 due to theincreased amount of foreign material and particulate matter 600 on theinner surface of the screen 40.

In another embodiment, the control system 90 may receive signalsproportional or representative of the differential pressure across thepump 120, with a larger differential pressure (due to lower inletpressure) providing another indication of the restriction or resistanceto oil flow through the screen 40. In yet other embodiments, the controlsystem 90 may receive an input signal proportional or representative ofthe pressure (or vacuum) at the suction 122 of the pump 120.

In some embodiments, for example, the control system 90 may cause thepiston 50 to translate through the housing 30 when the pump suction 122pressure or vacuum reaches a level between 0 and 15 inches of mercury.More specifically, the control system 90 may actuate when the pumpsuction 122 pressure or vacuum reaches between approximately 3 to 5inches of mercury. In still other embodiments, the control system 90 mayreceive a signal proportional to the mass flow rate of the oil leavingthe outlet aperture 33 b of the housing 30 and entering the pump 120suction 122 as measured by an internal flow meter.

The control system 90 is programmed to selectively cause rotation of thethreaded rod 62 (by operation of the motor 64 and clutch 66 (whenprovided) to cause the piston 50 to translate through the screen 40 uponan indication that the restriction or resistance to oil flow through thefilter 20 has increased above a certain threshold. The control system 90includes software and/or hardware that is programmed with logic tocontrol the operation of the threaded rod 62 based on the input positionand oil pressure or flowsignals, discussed above.

The control system 90 causes the threaded rod 62 to rotate in one of thetwo rotational directions depending on the position of the piston 50within the screen 40 and the direction that the piston most recentlymoved along the length of the screen 40. Specifically, the controlsystem 90 may operate to ensure that piston 50 reciprocates in a firstdirection Z (FIGS. 6a-7b ) along the length of the screen 40 to contactthe first end cup 70 and then translate in the opposite second directionY of the screen 40 to contact the second end cup 70. This ensures thatparticulate matter 600 on both sides of the piston ring 52 is eventuallyexpelled from the filter 20 through the slots 36 a in the collars 36,allowing for particulate removal in both directions of travel. In someembodiments, the control system 90 may include a set delay time tomaintain the piston 50 at one of the two extended positions (FIGS. 6b,7b ) for a set period of time to allow adequate time for the particulatematter 600 between the piston 50 and the end cap 70 to be expelled fromthe filter 20. In some embodiments, the control system 90 may include aroutine where the piston 50 causes and additional outward motion of theend cap 70 after returning to the housing 30 to further expelparticulate matter 600 that may remain between the piston 50 and the endcap 70 after the first removal cycle.

An exemplary logic diagram for the operation of the control system 90 isprovided in FIGS. 24a-24d . Initially, the control system checks to seewhether the oil within the vat 14 is at nominal operational temperatureusing an internal RTD, thermocouple, or other type of temperature sensor(not show). If needed, the control system 90 selectively operates theoil pump 120 to circulate oil through the internal piping as shown instep 710 while adding heat to the oil from the heat exchanger 130 (orelectric heaters 144). During this initial circulation, the oil pump 120may initially operate at slower speeds to circulate less oil until theoil temperature increases and the oil becomes less viscous.

Upon initial startup, the control system 90 checks to see whether thepiston 50 is at the normal starting position by checking the position ofa limit switch at the starting position, as in step 720. If the piston50 is not at this starting point, the control system 90 operates themotor 64 to rotate the threaded rod 62 to translate the piston 50 to thestarting position in accordance with FIG. 26. Upon reaching the startingposition, the control system monitors to see if an operation signal isobtained as in step 730. As discussed herein the operation signal may befrom a pressure of vacuum sensor, a pressure sensor, a flow sensor, orthe like and the operation signal is received whenever the monitoredparameter reaches a point that is representative of increased resistanceto oil flow due to significant screen 40 blockage.

Upon sensing the operation signal, the control system determines thedirection that the piston 50 should move, based on the position of theforward flag in step 740. When the piston is at the starting position,the forward flag will be on, and when not at the starting position (i.e.in situations after the first piston cycle to the second end 332 of thehousing 330) where the forward flag will be off.

Upon sensing the direction for piston 50 based on the position of theforward flag, the control system 90 energizes the motor 64 to rotate thethreaded rod 62 to translate the piston 50 to the opposite side of thehousing 30, as in step 750 or step 755 (depending on the position of theforward flag). While the piston 50 translates through the housing 30,the control system 90 monitors the movement of the piston 50 using thestructure discussed above. When the piston 50 comes close to reachingthe opposite end of the housing 30, the control system 90 may decreasethe rotational velocity of the piston 50 as in step 760 (765). When thepiston 50 approaches an end of the housing 30, the piston 50 directly orindirectly (with particulate matter 600 therebetween) contacts therespective end cap 70 and with additional piston 50 motion extends theend cap 70 away from the housing 30.

Eventually, the control system 90 senses that the piston 50 has reachedits outer limit of piston 50 travel and the control system 90 stops themotor 64 and the threaded rod 62. The control system 90 may allow thepiston 50 and end cap 70 to be maintained at this position to allow theparticulate matter 600 to be expelled or drain from the housing 30.

After a time delay, the control system 90 causes rotation of thethreaded rod 62 in the opposite direction, translating the piston 50 inthe opposite direction toward the opposite end cap 70, as shown in step770 (775). This piston 50 translation allows the end cap 70 to return toits normal position due to the biasing force of the biasing member 78 toagain provide an oil seal to the respective end of the housing. Aftersufficient inward movement of the piston 50 as sensed by the controlsystem 90, the control system 90 stops piston movement and maintains thepiston 50 at that position within the housing 30, and returns to step730 where the control system 90 monitors for an operation signal inaccordance with step 730. As discussed above, the fryer 10 may includededicated drive motors for both the oil pump 120 and the threaded rod62, which are operated by the control system in accordance with FIG. 25aand an alternate embodiment shown in FIG. 25 b.

In some embodiments, the control system 90 may have manual inputs toallow the user to order the control system 90 to move the piston 50within the screen 40, regardless of the position of the piston 50 or theoperational parameters of the filter 20. In yet other embodiments, thecontrol system 90 may include a time clock that controls the operationof the piston 50 at specified preprogrammed or user defined timeintervals or cook cycles, in addition to or in place of the operationalinputs of the filter 20 and the position inputs of the piston 50.

A pump 120 is fluidly connected to the output aperture 33 b of thehousing 30. Specifically, a suction, or inlet, 122 of the pump 122 isfluidly connected to the output aperture 33 b of the housing 30, suchthat the operation of the pump 120 pulls or drags oil from within theinternal volume 44 of the screen 40 through the plurality of holes 46,into the annulus 39 and eventually through the output aperture 33 b tothe inlet 122 of the pump 120. In one embodiment, at least one of theoutput apertures 33 b of the housing 30 is located so as to allow steamthat may have been entrained in the oil to be vented from the housing 30by the oil pump 120. The oil discharges from the pump 120 at an elevatedpressure that provides the motive force for oil to travel through theheat exchanger 130 and return at a higher temperature to the vat 14 forcooking food product.

In operation, the piston 50 is initially located at an initial positionwithin the internal volume of the screen 40. With operation of the pump120, oil that gravity drains into the internal volume 44 of the screen40 is urged through the plurality of holes 46 defined in the surfacearea of the screen 40 due to the suction forces of the pump 120. Withcontinued operation, a significant amount of foreign particulate matter600 builds up on the inner surfaces of the screen 40 because theparticulate matter 600 could not fit through the relatively smallminimum diameter of the plurality of holes 46.

With operation and collection of particulate matter 600 on the internalsurface of the screen 40, the restriction or resistance to oil flowthrough the screen increases due to blockage of the plurality of holes46. The control system 90 detects this increased resistance, asdiscussed above. When the monitored system resistance reaches apredetermined level (either preprogrammed at the factory, or a userdefined level) the control system 90 generates an operation signal inaccordance with step 730 of FIG. 24a , and rotates the threaded rod 62in one of the two rotational directions. The rotation of the threadedrod 62 causes the piston 50 to translate in the specific direction Y, Zalong the inner volume of the screen 40. The piston ring 52 scrapesagainst the inner surface of the screen 40 removing particulate matter600 and restoring the oil flow through the plurality of holes 46. Withthe blockage of the screen 40 removed, the restriction or resistance tooil flow through the filter 20 decreases.

With continued motion of the piston 50, the particulate matter 600 thatwas scraped from the screen 40 is pushed toward one of the two end cups70. During its translation, the piston 50 travels along the length ofthe screen 40. The piston 50 does not completely block the flow of oilthrough the screen 40 during its travel. As the piston approaches theinner surface 71 of the end cup 70, the piston 50 directly or indirectly(through contact with the particulate matter 600 therebetween, (shownrepresentatively and schematically in FIGS. 18b and 23 of theembodiments discussed below), forces oil out of the particulate matter600 due to the compressive force felt by the particulate matter 600. Theoil flows radially outward and through the plurality of holes 46 in thescreen 40. Eventually, the piston 50 contacts the inner surface 71 ofthe end cup 70 or indirectly contacts the end cup 70 (with particulatematter 600 therebetween). With continued rotation of the threaded rod 62in the same direction, the piston 50 urges the end cup 70 away from theopposing end cup 70 against the biasing force of the biasing member 78.During this motion the particulate matter 600 that was scraped from thescreen 40 by the piston ring 52 is retained between the piston 50 andthe end cup 70. With sufficient motion of the piston 50 to the removalposition (FIGS. 6b, 7b ), the contact point between the piston 50 andthe end cup 70 is located over the slot 36 c in the collar 36, whichallows the particulate matter 600 between the two members to gravitydrain from the filter 20 through the slot 36 c. Further, as the piston50 moves the end cup 70 away from the housing 30, the inward biasingforce on the end cup 70 increases, which similarly increases thecompressive forces felt by the particulate matter 600 between the piston50 and end cup 70. Eventually, the compressive force on the particulatematter 600 may increase above the compressive strength of theparticulate matter (when in a block or solid form), causing theparticulate matter 600 to crumble and be expelled from the housing 30through the slot 36 c.

As discussed above, the control system 90 receives signals that areproportional to or representative of the position of the piston 50within the screen 40 and with respect to each of the slots 36 c definedon the collars 36. When the control system 90 senses that the face ofthe piston 50 is above the slot 36 c, the control system 90 stops therotation of the threaded rod 62. After a short delay time to allow allof the particulate matter 600 to gravity drain through the slot 36 c,the control system 90 causes the threaded rod 62 to rotate in theopposite rotational direction. This rotation causes the piston 50 totranslate in the opposite direction, toward the center of the screen 40,which allows the end cup 70 to similarly translate toward the opposingend cup 70 due to the inward biasing force of the biasing member 78until the end cup 70 seals the respective end of the housing 30 with theassistance of the seal 75.

With sufficient linear motion toward the center of the screen 40, thepiston 50 is entirely disposed within the screen 40 and the end cup 70is restored to its operational position (FIGS. 6a, 7a ), where theinternal biasing force of the biasing member is minimized. When thepiston 50 reaches this position, the control system 90 receives a signal(in embodiments including limit switches) or processes the position ofthe piston 50 (in embodiments where the control system 90 counts therotations of the threaded rod 62), causing the control system 90 tosecure the rotation of the threaded rod 62 and maintain the piston 50 atthat position within the screen 40. The piston 50 remains at rest untilthe control system 90 senses another increase in flow restriction orresistance, wherein the control system 90 performs the same steps asdiscussed above to translate the piston 50 to the opposite end of thescreen 40 and remove additional foreign matter from the internal volumeof the screen 40 and push the particulate matter 600 out of the housing30 as discussed above.

Turning now to FIGS. 17-19, and alternate filter 220 is provided. Thefilter 220 includes a housing 230, a screen 240 disposed within thehousing 230, and a piston 250 that is translatably mountable within thehousing 230. The filter 220 is disposed below the vat 14 to receive oilfrom the vat 14 through an inlet aperture 233 a and into the internalvolume of the screen 240 through an inlet aperture 243 of the screen240. The screen 240 includes a plurality of holes 246 defined along themajority of the surface area of the screen 240 to allow oil to flowthrough the holes 240, but substantially prevent particulate matter 600(shown schematically in FIG. 18b ) entrained with the oil from flowingthrough the plurality of holes 240. The screen 240 may be substantiallythe same as the screen 40 discussed with respect to the previousembodiment.

The piston 250 is formed with a screen 255 that includes a plurality ofapertures 255 a defined on the leading face, or bottom surface, of thepiston 250. The screen 255 is formed similarly to the screen 240,wherein oil is free to flow therethrough, but particulate matter 600 issubstantially prevented from flowing through the second screen 255. Oilflowing through the screen 255 flows through the internal volume of thepiston and out the open trailing end of the piston 250. The piston 250includes at least one ring 252, which when compressed is substantiallythe same diameter as the internal diameter of the screen 240, whichallows the piston ring 252 to scrape the screen 240 to removeparticulate matter 600 adhered to the screen 240 with longitudinalrelative motion between the two.

The first end 231 of the housing 230 is enclosed with a cap 235 toprevent oil from leaving the housing 230 from the first end 231. The cap235 includes an aperture to allow the follower 260 (discussed below) toextend therethrough. The opposite second end 232 of the housing 230includes a plug 270 that is movably connected to the housing 230 with aspring or other biasing member 278. The plug 270 is normally biased to aposition where the plug 270 substantially blocks oil from leaving thehousing 230 from the second end 232. The plug 270 is longitudinallymovable along the housing against the biasing force of the spring 278when contacted by the piston 250, which allows the particulate matter600 between the plug 270 and the second screen 255 on the bottom surfaceof the piston 250 to be compressed, fracture (if in solid block-likeform) and be expelled or gravity drain) the housing 230 from a slot 236that becomes exposed when the plug 270 is sufficiently deflected (asshown in FIG. 18b ).

The piston 250 is urged longitudinally through the screen 240 and thehousing 230 with a follower 260 that pushes the piston 250. The follower260 may be mechanically connected to a motor (not shown) with a rack andpinion gear train (not shown), which translates rotation of the motorshaft (not shown) to linear motion of the follower 260. In otherembodiments, different structures and mechanisms that are known in theart may be provided to cause selective reciprocating linear motion ofthe piston 250 through the screen 240.

Similar to the embodiment discussed above, the filter 220 may beoperatively controlled by a control system 90 (similar to the controlsystem 90 discussed with respect to the embodiment above and shown inFIG. 20), which causes the piston 250 to translate through the screen240 when the control system 90 senses increase in flow resistancethrough the filter 220 due to mechanical blockage of the filter 240.When the control system 90 senses a sufficient increase in flowresistance (using at least some of the measured parameters discussedabove), the control system 90 activates the motor, which causes thepiston 250 to slide across the screen 240. The piston 250 scrapes theforeign particulate matter 600 from the screen 240, which becomesdeposited between the piston 250 and the plug 270.

Additionally, relatively pure oil flows through the screen 255 in thepiston 250, which deposits additional particulate matter 600 removedfrom the oil and prevented from flowing through the second screen 255between the piston 250 and the plug 270. With sufficient motion of thepiston 250, the piston 250 contacts the plug 270 and begins to translatethe plug 270 against the biasing force of the spring 278. The screen 240may not extend around the area of the housing 230 that supports the dualmotion of the piston and plug 250, 270, so oil between the piston andplug 250, 270 must flow through the screen 255 in the piston 250, whichreduces the oil content entrained between the two members.

With sufficient motion of the plug 270, a slot 236 in the housing 230 isexposed, which allows the particulate matter 600 to be forced or gravitydrain from the housing 230 into a pan (not shown) or another suitablestructure. The control system 90 then withdraws the piston 250 back tothe first end 231 of the housing 230 and awaits another operationalcycle. As the piston 250 is pulled away from the second end 232 of thehousing 230 by the follower 260, the plug 270 seals against the end ofthe housing 230 (with the assistance of a seal (not shown) disposed onone or both of the housing 230 and the plug 270, and is restored to itsinitial position by the spring 278.

Turning now to FIGS. 21-23, an alternate filter 320 is provided. Thefilter 320 includes a housing 330, hollow cylindrical screen 340 that iscoaxially disposed within the housing 330. A piston 350 is slidinglydisposed within the internal volume of the screen 340 such that theouter circumferential surface of the piston 350, or piston ring 352,contacts the inner surface of the screen 340 as the piston 350translates within the screen 340. The piston 350 is formed and operatedsimilarly to piston 50 discussed above. As with the first embodimentdiscussed above, the piston 350 translates within the screen 340 due tothe rotation of a threaded rod 362 that extends through the center ofthe piston 350, as controlled by the control system 90 discussed aboveand shown in FIG. 20.

End caps 370 are longitudinally movably mounted to each of the opposingfirst and second ends 331, 332 of the housing 330. The end caps 370 areinwardly biased by a spring 378 or other biasing member, which may beconstrained to the opposing end cap 370 or alternatively, dedicatedsprings 378 for each end cap 370 may be provided and secured to thehousing 330 or another rigid portion of the filter 320. As bestunderstood with reference to FIGS. 22 and 23, one of the two end caps370 is always disposed such that the end cap 370 provides a seal to anend of the housing 330 to substantially prevent oil leakage from therespective end of the housing 330 and the screen 340. When performingthe extraction process the opposite end cap 370 may be translatedlongitudinally outward away from the opposing end cap 370 until the endcap 370 no longer contacts the housing 330.

The outward longitudinal motion of the end cap 370 is constrained by ashoe 380 that is fixed to the outer end of the end cap 370 (i.e. the endfacing away from the opposing end cap 370). The shoe 380 is biasinglyengaged with the spring 378, which urges the shoe 380, and therefore theend cap 370) toward the opposing end cap 370. In some embodiments, aturnbuckle 388 may be disposed between an end of the shoe 380 and thespring 378, which allows the spring 378 to be adjusted by rotating theturnbuckle 388. Each end of the shoe 380 includes an aperture (notshown) that receives a guide rod 384 that is extendable between an endof the housing 330 and a cross-bar 382 to guide the longitudinalmovement of the end cap 370.

The end cap 370 is longitudinally movable away from the respective end331, 332 of the housing 330 due to the longitudinal movement of thepiston 350. An end of the piston 350 may directly contact the innersurface of the end cap 370 to urge the end cap 370 outwardly, or in someoperational situations the piston 350 may indirectly contact the end cap370 to urge outward motion with a chunk or volume of particulate matter600 (shown schematically as 600 in FIG. 23) disposed between the twomembers to transfer force from the piston 350 to the end cap 370. Theparticulate matter 600 may be in the form of a substantially solid blockor the particulate matter 600 may be granular.

As the end cap 370 is urged further and further from the end of thehousing 330 the particulate matter 600 becomes no longer enclosed withinthe housing 330 and becomes suspended between the piston 350 and the endcap 370 outside of the housing 330 due to the compressive force felt bythe particulate matter 600. Any particulate matter 600 that is in thegranular form may fall from between the piston 350 and the end cap 370to a pan or other retention member. With further compression (due to theincreasing inward biasing force on the end cap 370) the compressiveforces felt by any remaining chunks of particulate matter 600 similarlyincreases until the block yields to the force and crumbles to asubstantially granular form, or a plurality of smaller blocks.

After the particulate matter 600 crumbles or yields, a substantialportion is free to fall from between the piston 350 and the end cap 370due to gravity. As the particulate matter 600 is removed from the filtersystem 320, the end cap 370 moves toward the piston 350 due to theoutward biasing force on the end cap 370.

After substantially all particulate matter 600 is removed from betweenthe piston 350 and the end cap 370, the control system 90 rotates thethreaded rod 362 in the opposite direction to translate the piston awayfrom the end cap 370 and toward the center of the screen 340 for asufficient amount of inward piston 350 travel to allow the end cap 370to return to the end of the housing 330 due to the biasing force of thespring 378 and provide a seal on the end of the housing 330 tosubstantially prevent oil from leaking from that end of the housing 330.In some embodiments, the control system 90 may include a routine wherethe piston 350 causes and additional outward motion of the end cap 370after returning to the housing 330 to further expel particulate matter600 that may remain between the piston 350 and the end cap 370 after thefirst removal cycle.

As discussed above, the control system 90 monitors the operationalparameters of the filter 320 and eventually causes the piston 350 totranslate to the opposite end of the housing 330 to remove particulatematter 600 from the inner surface of the screen 340 and ejection betweenthe piston 350 and the opposite end cap 370.

Turning now to FIGS. 27-32, an alternate cooking appliance is provided.The cooking appliance may be a deep fat fryer 1700, or another type ofcooking appliance, such as a pasta cooker or rethermalizer, where a foodproduct is cooked in a volume of heated liquid. One of ordinary skill inthe art will recognize that the disclosure herein can be usedsuccessfully on other machines where there is a need to continuouslyremove particulate matter from a volume of liquid therein and/or provideheat to the liquid after removing particulate matter from the liquid.

The fryer 1700 is constructed similarly to the fryer 10 discussed aboveand components with like element numbers are similar to those similarcomponents discussed above. The fryer 1700 includes a housing 12 thatmechanically supports all of the components of the fryer 1700 and a vat14 that provides an open volume for storing and heating a quantity ofcooking oil for frying a food product placed therein. In other types ofcooking appliances the vat 14 is configured to store other liquids thatare heated to cook a food product. The fryer 1700 further includes aheat source 15 that provides heat to the cooking oil stored within theopen vat 14. The heat source may be a provided by burning natural gas orsimilar fuel in an open flame that heats air passing through the fryer1700, or alternatively, the heat source may be provided by a pluralityof electrical heaters (not shown) that are disposed in the proximity ofthe vat 14 or another portion of the fryer 1700 where heat from theheaters may be transferred to the oil of the fryer 1700. The componentsof the fryer 1700 and the continuous filter system discussed herein areoperated by the control system 91 (FIG. 20a ). The detailed logicdrawings of the control system 90 discussed above and shown in FIGS.24a-24d are illustrative of the logic methodology used to operate thecontrol system 91.

The fryer 1700 includes a primary filter 1720, a secondary filter 1790assembly, and an oil circulation system 1810 that allows oil toselectively flow from the vat 14 through one or both of the secondaryfilter assembly 1790 and the primary filter 1720, a pump 120 and heatexchanger 130, and return to the vat 14. Oil flow through the oilcirculation system 1810 is urged with a pump 120 that may be disposedbetween the primary filter 1720 and secondary filter assembly 1790 andthe heat exchanger 130.

As best shown in FIG. 28, the pump 120 draws a suction from one of thetwo potential oil flow paths, either a primary branch 1822 drawingsuction from the primary filter 1720, or urging oil through a secondarybranch 1832, which draws suction upon a secondary screen 1794 in thesecondary filter assembly 1790. The pump 120 is discussed in furtherdetail below.

As discussed in greater detail below, the oil circulation system 1810includes five branches configured for oil flow therethrough. An inletbranch 1812 allows oil to gravity drain from the vat 14 to the inlet1792 of the secondary filter assembly 1790. A discharge path 1852 isconfigured to allow oil to flow from the discharge 124 of the pump 120to the heat exchanger 130 and ultimately return to the vat 14. In otherembodiments, the inlet branch 1812 may include a pump (not shown) tourge oil from the vat 14 to the secondary filter assembly 1790.

A primary oil flow branch 1822 extends from a normal oil outlet 1793 ofthe secondary filter assembly 1790 through the primary filter 1720 andto the pump suction 122. A drain valve 1826 may be provided between anormal outlet 1793 of the secondary filter assembly 1790 and the oilinlet 1733 a of the primary filter 1720 and is operable to selectivelyprevent oil flow between the secondary filter assembly 1790 and theprimary filter 1720. The drain valve 1826 is normally open, but can beshut to secure the oil flow through the primary filter 1720 depending onthe position of the piston 1750 within the housing 1730, as discussedbelow.

In other embodiments shown in FIGS. 33-35 a, the piston 1750 or analternate piston 1750 a (discussed in greater detail below) may includea skirt 1757 that extends rearwardly from the front face 1754 of thepiston 1750 (or front face 1754 a of the piston 1750 a). The skirt 1757is a cylindrical, hollow tube with an inner diameter slightly less thatthe inner diameter of the screen 1740. The skirt 1757 is configured toblock the inlet aperture 1733 a of the housing 1730 and the inletaperture 1743 of the screen 1740 when the front face 1754 of the piston1750 is disposed between the inlet aperture 1733 a and the operationalend 1732 of the housing 1730. The skirt 1757 accordingly prevents oilfrom entering the internal volume of the housing 1730 behind the piston1750, wherein any particulate matter filtered from the oil through thescreen 1740 and disposed between the piston 1750 and the end plug 1761cannot be removed during normal operation of the primary filter 1720.The skirt 1757 may include one or more rings (not shown but similar torings 52 discussed above) that are configured to scrape against theinner surface of the filter 1740 to remove particulate matter therefrom.

A secondary oil flow branch 1832 is disposed between a secondary outlet1796 of the secondary filter assembly 1790 and the pump suction 122,which allows oil flow to the pump 120 when the drain valve 1826 is shut(i.e. oil is prevented from flowing through the primary filter 1720) orthe skirt 1757 of the piston 1750 blocks the oil inlet aperture 1733 a.A secondary inlet valve 1836 is provided between the secondary outlet1796 of the secondary filter assembly 1790 and the pump 121. Thesecondary inlet valve 1836 is normally shut, but can be open to allowflow from the secondary filter assembly 1790, through the secondaryscreen 1794 and to the pump suction 122 when the drain valve 1826 isshut. Operating with the secondary inlet valve 1836 open and the drainvalve 1826 shut maintains oil flow through the heat exchanger 130, andadditionally filters the oil within the oil circulation path 1810 by thesecondary screen 1794, discussed below.

A back purge branch 1842 is disposed between the pump discharge 124 anda secondary oil inlet 1797 within the secondary filter assembly 1790. Aback purge valve 1846 is provided within the back purge branch 1842 andis normally shut. The back purge valve 1846 is opened for a limited timeafter the secondary inlet valve 1836 has cycled open and then shut. Whenthe back purge valve 1846 is opened, oil flows through the secondary oilinlet 1797 of the secondary filter assembly 1790, and specifically oilflows through the secondary screen 1794 in the direction R opposite fromthe direction P of oil flow through the secondary screen 1794 when thesecondary inlet valve 1836 is opened. As discussed in greater detailbelow, the reverse oil flow through the secondary screen 1794 dislodgesany particulate matter or debris adhered to an inner surface of thesecondary screen 1794 (i.e. debris or particulate matter removed fromoil flowing in direction P through the secondary screen 1794), andcauses the removed debris or particulate matter to flow to the primaryfilter 1720 to ultimately be removed from the fryer 1700.

Each of the drain valve 1826, the secondary inlet 1836, and the backpurge valve 1846 may be automatically operated upon receipt ofoperational signals from the control system 91, without requiring anymanual operator action. Each of the valves 1826, 1836, 1846 may be ballvalves, gate valves, butterfly valves, or other types of valves thatprovide for selective isolation of the corresponding flow path, butprovide little head loss or resistance to flow with the correspondingflow path when opened. In some embodiments, the valves may be solenoidoperated, motor operated, or operable with other mechanical orelectrical devices known to selectively and reliably operate a valve.

Turning now to FIGS. 29-29 a, the secondary filter assembly 1790includes an inlet 1792, a normal oil outlet 1793, and a screen 1794disposed therein. The screen 1794 is constructed similarly to the screen40 discussed in the embodiments above, with some differences notedbelow. The screen 1794 includes a plurality of apertures 1794 a to allowoil to flow therethrough but prevent debris and particulate matter fromflowing therethrough. The apertures 1794 a may be sized, shaped, andconfigured upon the screen 1794 similarly to the apertures 46 discussedherein with respect to screen 40. Alternatively, the apertures may belarger or smaller and the total area available for oil flow through thescreen may vary depending on the desired filtering with the secondaryscreen.

As shown in FIG. 27, the secondary screen 1794 is hollow and cylindricaland extends between the inlet 1792 and the normal oil outlet 1793 of thehousing 1791 to constrain flow therebetween. In contrast to the screen40 discussed above, the secondary screen 1794 does not include an inletaperture 43. The inner volume of the screen 1794 is in fluidcommunication with the inlet 1792 of the secondary filter assembly 1790,such that all oil entering the inlet 1792 flows through the lumendefined by the inner volume of the screen 1794.

The secondary filter assembly 1790 additionally includes a channel 1795disposed between an outer surface of the secondary screen 1794 and thehousing 1791. A secondary outlet 1796 and a secondary inlet 1797 areeach disposed within the housing 1791 in fluid communication with thechannel 1795. During normal operation of the fryer 1700, the drain valve1826 is open (and/or the skirt 1757 of the piston 1750 does not blockthe oil inlet aperture 1733 a of the housing 1730) and the secondaryinlet and back purge 1836, 1846 valves are shut. In this configuration,the screen 1794 is not directly fluidly connected with the pump 120 andthe oil entering the secondary filter assembly 1790 from the vat 14flows through the normal outlet 1793 to the primary filter 1720, becausethere is no differential pressure across the secondary screen 1794 toforce oil through the plurality of apertures 1794 a.

When one of the secondary inlet or back purge valves 1736, 1746 areopen, the respective suction 122 or discharge 124 of the pump 121 isfluidly connected with the channel 1795 of the housing 1791, and oilthrough the screen either in direction P or R as schematically shown inFIGS. 29 and 29 a. As discussed above, oil flow in the schematicdirection P removes particulate matter from the oil, which may becomedeposited on the inner surface of the secondary screen 1794 andgradually degrade the flow rate through the secondary screen 1794.Opening the back purge valve 1846 causes flow in the reverse direction Rthrough the secondary screen 1794, which substantially dislodges debrisand particulate matter form the inner surface of the secondary screen1794.

As best shown in FIG. 29a , the inlet 1792 and the normal outlet 1793 ofthe secondary filter assembly 1790 are defined by apertures in oppositeends of the housing 791. Seals 1799 may be provided within the housing1791 at each end thereof to prevent oil leakage from the housing 1791through the ends. Seals 1799 may be o-rings, gaskets, or otherstructures known to substantially prevent fluid leakage.

A primary filter 1720 assembly is provided and is best shown in FIGS.30-32. The primary filter 1720 includes a housing 1730, a primary screen1740, a piston 1750 that selectively translates within the housing 1730,a fixed end plug 1761, a movable end cap 1770, and a reciprocating leg1780. The primary screen is similar in operation and design of thescreen 40 discussed herein and shown in FIGS. 6a-7b and 9 and for thesake of brevity, the screen will not be discussed again in detail.

The housing 1730 is cylindrical, hollow and extends between a home end1731 and an operational end 1732. The housing 1730 is similar in designand construction to the housing 30 discussed above. The primary screen1740 is fixed within the housing 1720, similar to the screen 40 withinthe housing 30, discussed above. The housing 1730 additionally includesan annulus 1739 (FIGS. 35-35 a) that is disposed between an outersurface of the primary screen 1740 and the housing 1730. The annulus1739 is similar to annulus 39 discussed in the embodiments herein andoriginates the portion of the primary oil flow branch 1822 between theprimary filter 1720 and the pump suction 122.

The housing 1730 includes an end plug 1761 fixed to the home end 1731and a movable end cap 1770 retained at the opposite operational end 1732of the housing 1730. The end plug 1761 provides a substantially leaktight boundary of the housing 1730 and includes holes therein for thelead screw 1762 (similar to the lead screw 62 discussed above) and thesecond rod 1768 (similar to the second rod 68 discussed above) to extendtherethrough. The piston 1750 rests proximate the end cap 1761 when thepiston 1750 is in the home position.

Oil normally enters the primary filter 1720 through an inlet aperture1733 a in the housing 1730 and flows into the center of the screenthrough an inlet aperture in the screen, similar to the filter 20discussed herein. The primary filter 1720 normally is fluidly connectedwith the pump suction 122 (i.e. when the drain valve 1826 is open or theskirt 1757 does not block the oil inlet aperture 1733 a on the housing1730) which provides a significant differential pressure across theprimary screen 1740. The differential pressure causes oil to flowthrough the plurality of apertures 1746 in the primary screen 1740, intothe annulus 1739, and ultimately to the pump suction 122 through theprimary oil flow branch 1822.

As discussed above with respect to the screen 40, the plurality ofapertures 1746 within the primary screen 1740 may be sized to preventdebris and particulate matter larger than the apertures entrained withthe oil (due to the frying within the vat 14 or other cooking processfor other types of cooking appliances) from flowing through the primaryscreen 1740 with the oil. The debris and particulate matter retainedwithin the primary screen 1740 may stick to the inner surface of theprimary screen 1740 (thereby gradually lowering the oil flow through theprimary filter 1720 due to the reduction in available flow area throughthe primary screen 1740). The debris and particulate matter isperiodically removed from the screen by the piston 1750.

The piston 1750 is translatably received within the housing 1730. Thepiston 1750 may include one or more rings (not shown, but similar torings 52 discussed herein) that are configured to scrape across theinner surface of the screen to remove debris and particulate matterstuck to the inner surface of the primary screen 1740. The piston 1750is cylindrical and includes a front face 1754 (FIG. 31) and a rear face.The front face 1754 of the piston 1750 is oriented within the housing1730 to contact the cup 1772 a of the end cap 1770 when the piston 1750is at the operational end 1732 of the housing 1730 and the rear face isoriented to face and remain proximate the end plug 1761 when the piston1750 is in the home position. The front face 1754 of piston 1750 may beconfigured similarly to the faces of the piston 50.

As discussed below and understood with reference to FIGS. 28 and 30-32,the piston 1750 is configured to remove a significant amount ofparticulate matter from the inner surface of the primary screen 1740when linearly translating from the home end 1731 toward the operationalend 1732 of the housing 1730. The piston 1750 cyclically translates fromthe home position (i.e. proximate the home end 1731 of the housing 1730)to the operational end 1732 to contact and translate the inner flange1772 of the end cap 1770 away from the housing 1730 for disposal ofparticulate matter 600 therebetween from the primary filter 1720. Thepiston 1750 then returns to the home position and awaits anothertranslational cycle as signaled by the control system 91.

Because the primary filter 1720 only includes structure for removal ofdebris one the operational end 1732 of the housing 1730, the fryer 1700is configured to substantially prevent oil (and particulate matterentrained therewith) from entering the primary filter 1720 when thefirst face 1754 of the piston 1750 is between the operational end 1732and the inlet opening 733 a. In some embodiments, the drain valve 1826is configured to shut (as controlled by the control system 91) when thefront face 1754 of the piston 1750 translates past the inlet aperture1733 a of the housing and the inlet of the screen toward the operationalend 1732 of the housing 1730. Because no oil flows into the housing 1730from the secondary filter assembly 1790, particulate matter is notdeposited between the piston and the fixed end plug 761 of the housing1730. When the drain valve 1826 shuts, the secondary inlet valve 1836opens providing flow to the pump suction 122 through the secondaryfilter 1794.

In other embodiments shown in FIG. 33-35 a, the piston 1750 or analternate piston 1750 a (discussed in greater detail below) may includea skirt 1757 that extends rearwardly from the front face 1754 of thepiston 1750 (or front face 1754 a of the piston 1750 a). The skirt 1757is a cylindrical, hollow tube with an inner diameter slightly less thatthe inner diameter of the screen 1740. The skirt 1757 is configured toblock the inlet aperture 1733 a of the housing 1730 and the inletaperture 1743 of the screen 1740 when the front face 1754 of the piston1750 is disposed between the inlet aperture 1733 a and the operationalend 1732 of the housing 1730. The skirt 1757 accordingly prevents oilfrom entering the internal volume of the housing 1730 behind the piston1750, wherein any particulate matter filtered from the oil through thescreen 1740 and disposed between the piston 1750 and the end plug 1761cannot be removed during normal operation of the primary filter 1720.The skirt 1757 may include one or more rings (not shown but similar torings 52 discussed above) that are configured to scrape against theinner surface of the filter 1740 to remove particulate matter therefrom.

The piston 1750 may translate linearly through the internal volume ofthe housing 1730 due to the rotation of the lead screw 62, which issimilar to the lead screw 62, discussed above. The lead screw 62 isrotatably connected with a transmission 63, which receives torque from amotor 64. As discussed above, the motor 64 may be a dedicated motor forthe lead screw 62, or alternatively, the motor 64 may the same motorthat rotates the pump 120. In embodiments where the same motor rotatesboth the pump 120 and the lead screw 62, a clutch is provided betweenthe motor and the lead screw 62 to causes selective transmission oftorque from the motor to the lead screw 62, depending on the operationalperformance of the primary filter 620, as discussed below. The clutch isconfigured to causes the motor to rotate the lead screw 62 in eitherrotational direction.

The piston 1750 includes a threaded aperture that receives the leadscrew 1762. The piston 1750 further receives a second rod 1768therethrough, which prevents the piston 1750 from rotating with rotationof the lead screw 1762. Because the piston 1750 is prevented fromrotating, the piston 1750 translates linearly within the internal volumeof the housing 1730 based on the direction of the rotation of the leadscrew 1762.

In other embodiments shown in FIGS. 33-35 b, an alternate piston 1750 amay be disposed within the housing 1730 and operates similarly to thepiston 1750 discussed above. The piston 1750 a includes a flat frontface 1754 a that is disposed to cyclically contact the inner flange1772, and specifically the cup 1772 a similarly to the piston 1750discussed herein. A skirt 1757 may be received upon the piston 1750 toselectively block the inlet aperture 1733 a of the housing 1730 when thefront face 1754 a of the piston 1750 a is between the inlet aperture1733 a and the operational end 1732 of the housing 1730.

The piston 1750 a includes a central aperture 1755 a (or blind hole thatdoes not extend through the entire width of the piston 1750 a) that isconfigured to receive a shaft 1758 that extends toward the end cap 1761of the housing 1730. The shaft 1758 is connected with a nut 1759 thatthreadably receives a lead screw 1762 a. The lead screw 1762 a isconnected to the transmission 1763 and the motor 1764 to selectivelyrotate the lead screw 1762 a to cause the piston 1750 a to translatelinearly within the housing 1730 to scrape debris from the inner surfaceof the screen 1740. The nut 1759 includes a plurality of flats 1759 a orother structures that engage the housing 1730 to prevent the nut 1759from rotating. As the lead screw 1862 a rotates, the nut 1759 translateslinearly within the housing, which causes similar motion of the piston1750 a.

Similar to the embodiments discussed above, in some embodiments therotation of the motor 64 (and therefore translation of the piston 1750)is controlled by the control system 91, which receives operationalsignals from the fryer 1700 related to the mass flow rate through thepump 120 and proportional to the flow area available through the primaryscreen in the primary filter 1720. When the control system 91 senseslower flow through the pump 121, the piston 1750 is translated towardthe operational end 1732 of the housing 1730 to mechanically remove theparticulate matter from the screen increase flow though the oilcirculation system 1810. The various parameters potentially monitored bythe control system 91 for selective cyclic operation of the piston 1750are discussed elsewhere herein and are not repeated here for the sake ofbrevity.

The end cup 1770 includes two parallel plates, an inner flange 1772 andan outer flange 1774 that are separated by a plurality of springs 1775or other biasing members. The outer flange 1774 is movably fixed at aset distance from the operational end 1732 of the housing 1730 and maybe translated further away from its fixed position with respect to thehousing 1730 with a first translation device 1779.

The inner flange 1772 is biased toward the housing 1730 with pluralityof biasing members 1775. The inner flange 1772 includes a cup 772 a thatnormally extends within the hollow internal volume of the housing 1730and an end portion of the screen. The cup 772 a and the inner flange 772normally provide a leakage barrier for the operational end 732 of thehousing 1730. The cup 1772 a and the inner flange 1772 may includes agasket, o-ring, or other mechanical structure to substantiallycompletely seal the operational end of the housing 1732, when the innerflange 1772 is in the normal position shown in FIG. 30.

In some embodiments, the end cup 1770 is selectively linearly translated(toward or away from the operational end 1732 of the housing 1730) witha translation device 1779. The translation device 1779 may be motor witha threaded shaft that causes linear translation of the outer flange 1774based on the rotation of the motor, a linear actuator (FIGS. 30-32) witha shaft 1778 fixedly mounted to the outer flange 1774 that provides forselective linear motion of the end cup 1770, one or more solenoids orother forms of electromagnets, or other mechanical and electromechanicalstructures that cause selective linear motion of the end cup 1770 towardand away from the housing 1730. The end cup 1770 translation may beguided by a plurality of shafts 1776 and a bracket 1777 that areconnected therewith.

A leg 1780 is reciprocatingly mounted with respect to the operationalend 1732 of the housing 1730 to cyclically move proximate theoperational end 1732 of the housing 1730. The leg 1780 may include anoperational end 1782 that extends radially from a pinned connection 1786with the housing 1730. The operational end 1782 is configured toreciprocate downward between the piston 1750 and the cup 1772 a toremove any particulate matter disposed between the piston 1750 and thecup 1772 a. The operational end 1782 may include two parallel outersurfaces, and may additionally include one or more brushes, or elasticstrips or other members on the outer surfaces thereof to scrape orotherwise remove particulate matter affixed to the front face 1754 ofthe piston 1750 or the outer surface of the cup 1772 a.

The leg 1780 may be reciprocatingly movable with respect to the housing1730 with a linear actuator, motor, solenoid or other electromagnet, orother structure to automatically cause the leg 1780 to reciprocate. Asshown in FIG. 32, a linear actuator 1784 may be provided with an outputarm 1784 a constrained with the leg 1780, such that inward motion of theoutput arm 1784 a (i.e. toward the linear actuator 1784 housing) causesthe operational end 1782 of the leg 1780 to rotate about a pinnedconnection with the housing 1730 between the piston 1750 and the cup1772 a and mechanically remove any particulate matter therebetween. Theoutput arm 1784 a of the linear actuator 1784 is then translatedoutward, causing the operational end 1782 to withdraw from between thepiston 1750 and the cup 1772 a. In some embodiments, the control system91 is operationally connected with the linear actuator 1784 to cause theleg 1780 to reciprocate one or more times with respect to the piston1750 when the end cup 1770 is fully withdrawn from the housing 1730 tothe position shown in FIG. 32.

In some embodiments, the translation device 1779 and the linear actuator1784 may be distinct dedicated components that provide a motive force totranslate or rotate the outer flange 1774 and the leg 1780,respectively. In other embodiments, each of the outer flange 1774 andthe leg 1780 may be selectively operated by the same mechanical device,such as for example a motor, linear actuator, electromagnet or otherdevice to selectively operate the outer flange 1774 or leg 1780. With acommon device for each of the outer flange 1774 and the leg 1780, aclutch (not shown) or other selective transmission device is disposedbetween the common device and each of the outer flange 1774 and the leg1780 to allow selective operation. In still other embodiments, the outerflange 1774, leg 1780, lead screw 1762, and/or the pump 120 may beoperated by the same motor or other mechanical and/or electrical device,with clutches (or other selective transmission device) disposed betweenthe device and the movable component.

In operation, after sufficient fryer operation, the flow through thepump 120 may degrade such that the control system 91 initiates a cycleof the piston 1750. The piston 1750 translates through the housing 1730and scrapes any particulate matter or debris from the inner surface ofthe screen. As the piston 1750 approaches the operational end 1732 ofthe housing 1730, a volume of particulate matter 600 may be disposedproximate the front face 1754 of the piston 1750. With furthertranslation of the piston 1750, the piston 1750 contacts the cup 1772 aon the inner flange 1772 of the end cap 1770 (either directly or withparticulate matter therebetween).

With further rotation of the lead screw 1762, the piston 1750 pressesthe inner flange 1772 toward the outer flange 1774. Initially, the forceon the inner flange 1772 is less than the biasing force of the springs1775 and further piston 1750 translation causes further compression ofthe inner flange 1772 and any particulate matter disposed therebetween.The additional compression tends to squeeze any oil that remains withthe particulate matter (because of the relative incompressibility of theoil), which flows through apertures of the screen into the annulus andultimately to the pump 120. With sufficient compression, the relativelydry particulate matter 600 tends to crumble and fall from the housingwhen exposed from the operational end 1732.

With additional motion of the piston 1750 toward the operational end 732of the housing 1730, the inner flange 1772 eventually feels a sufficientcompressive force to compress the springs 1775 and translate toward thefixed outer flange 1774. As the springs 1775 compress, the cup 1772 awithdraws from the housing 1730 (FIG. 31) and additional particulatematter 600 may drop from between the piston 1750 and the inner flange1772 due to gravity. The removed particulate matter 600 is retained by atray or similar structure (not shown) therebelow in the fryer housing 12for periodic removal. With the cup 1772 a withdrawn from the housing1730, the piston 1750 becomes the leakage boundary for the operationalend 1732 of the housing 1730 (although oil does not enter the housing1730 in this orientation due to the closure of the drain valve 1826).

In some embodiments, the housing 1730 may include a limit switch (notshown) or similar sensor in communication with the control system 91that senses when the cup 1772 a is withdrawn from the housing 1730.After the cup 1772 is pushed from the housing 1730 by the piston 1750,the end cup 1770 is translated away from the housing 1730 by thetranslation device 1779 to leave a space between the front face 1754 ofthe piston 1750 and the cup 1772 a of the inner flange 1772. In otherembodiments, the control system 91 may count the number of rotations ofthe lead screw 1762, and determine the position of the piston 1750within the housing 1730 and therefore the relative positions of the cup1772 a and the inner flange 1772 with respect to the housing 1730.

As the end cap 1770 is translated away from the housing 1730, a space isprovided between the front face 1754 of the piston 1750 and the cup 1772of the inner flange 1772. The control system 91 then causes theoperational end 1782 of the leg 1780 to cyclically move between thepiston 1750 and the cap 1772 a, which pushes any remaining particulatematter 600 away from between the two components and additionally mayclean the ends of the components. After one or more cycles of the leg1780, the operational end 1782 of the leg 1780 is withdrawn and thetranslation device 1779 moves the end cap 1770 toward the housing 1730until the cap 1772 a contacts the piston 1750. The control system 91then causes rotation of the lead screw 62 to translate the piston 1750toward the home position.

When the front face 1754 of the piston 1750 moves past the inletaperture 1733 a of the housing 1730 and the screen, the drain valve 1826opens allowing oil flow from the secondary filter assembly 1790 to enterthe primary filter 1720. At the same time, the secondary inlet valve1836 shuts, securing flow through the secondary screen 1794 (in thedirection P) to the pump suction 122. The back purge valve 1846 thentemporarily opens, allowing flow from the pump discharge 124 (in thedirection R), which removes any particulate mater fixed to the secondaryscreen 1794, which flows to the primary filter 1720 for removal.

Turning now to FIGS. 38-49, an alternate cooking appliance 800 isprovided. The cooking appliance 800 may be a deep fat fryer, arethermalizer, a pasta cooker, bagel or donut fryer or another similarappliance that uses a heated cooking fluid to cook a food product, withthe cooking fluid requiring periodic cleaning, purifying, or filteringfor proper operation. While one of skill in the art will understandafter review of this specification, appended figures and claims that thecooking appliance may be one of a plurality of types of cookingappliances, for the sake of brevity this embodiment is described herewith reference to a deep fat fryer that cooks a food product disposedwithin a pool of heated oil disposed within a vat. Unless otherwisespecified, the components of the fryer are similar to the components ofthe fryer 10 discussed above and shown in FIG. 1.

The fryer includes a housing 12 that mechanically supports all of thecomponents of the fryer. The fryer includes a vat 14 that provides anopen volume for storing and heating a quantity of cooking oil forcooking a food product placed therein. The fryer further includes a heatsource 15 that provides heat to the cooking oil to maintain the cookingoil within the open vat 14 at a desirable temperature for cooking. Theheat source 15 may be provided by burning natural gas or similar fuel inan open flame that heats air passing through the fryer, oralternatively, the heat source may be provided by a plurality ofelectrical heaters that are disposed in the proximity of the vat 14 oranother portion of the fryer where heat may be transferred to thecooking oil. The fryer may additionally or alternatively include a heatexchanger 130 (FIGS. 1, 2, and 3) which continuously receives oil fromthe vat 14 by way of the filter mechanism 810 discussed below and thepump 120 (FIGS. 12-16 discussed herein) where air heated by the heatsource 15 flows past the heat exchanger 130 to transfer heat to the oilflowing therethrough. In other embodiments shown in FIG. 2a , the fryermay include an electric heater assembly 144 that receives oil from thepump 120 and provides heat to the oil flowing therethrough with one of aplurality of electric heaters 144 a.

It is advantageous to provide a sole heat input to the oil with the heatexchanger 130 (or electric heater assembly 144) because the heatingelements need not be placed directly within the vat 14. This allows thecapacity of the vat 14 to be reduced and therefore increases theefficiency of the fryer by eliminating the cold zone in the bottomportion of the typical fryer vat 14. The placement of the heating device(whether through combustion gas or electric heaters) outside of the vat14 (which may be provided in the flue section of a typical fryer) allowsthe vat and other portions of the housing 12 of the fryer to be ofuniform geometry and dimensions regardless of the type of heating deviceused. As understood by those of skill in the art, this reduces thenumber of different components necessary to manufacture both gas andelectric appliances and therefore increases manufacturing efficiency.

The filter mechanism 810 includes a primary filter assembly 811 thatcontinuously operates during fryer operation to remove debris andparticulate impurities from the oil received within the filter mechanism810. The fryer additionally includes a debris extraction mechanism 830that receives the debris and particulate impurities removed from the oilin the primary filter assembly 811 and ejects the particulate matterfrom the filter mechanism 810. The primary filter assembly 811 anddebris extraction mechanism 830 may be mounted within the fryer housing12 and normally are each disposed below the vat 14.

The primary filter assembly 811 receives a continuous flow of oil fromthe vat 14 through an inlet port 814. The inlet portion 814 is definedwithin a cover 813 that encloses an upper end of an main housing 812.The main housing 812 is substantially cylindrical with a longitudinalaxis 812 a that is disposed substantially vertically within the housing12. The main housing 812 includes an open lower end that is fluidlyconnected with a lower housing 831 of the debris extraction mechanism830, discussed below. A cylindrical main screen 816 is disposed withinthe main housing 812 and aligned coaxially therewith. The main screen816 includes a slightly smaller diameter than the inner diameter of themain housing 812 to define an annulus 818 between the inner housing 812and the main screen 816. The main screen 816 is constructed similarly tothe screen 40 (discussed above and shown in FIG. 9) and includes aplurality of holes 816 a that are constructed similarly to the holes 46in the screen 40. Because the main housing 812 and main screen 816 areeach aligned to receive oil flowing in a path parallel to the centerlinelongitudinal axis 812 of the main housing 812, the screen 816 does notnormally include an inlet aperture similar to the inlet aperture 43 ofthe embodiment discussed above. One of ordinary skill in the art willappreciate after reviewing this specification and appended drawings thatother geometries of the main housing 812 and main screen 816 arepossible, which may necessitate changes in the geometry and orientationof these and other associated components for proper orientation.

A suction port 122 of an oil pump 120 is fluidly connected with theannulus 818 by way of an outlet pipe 819 to urge oil from within thecavity 817 (i.e. within the inner diameter of the main screen 816)through the main screen 816, the annulus 818, and to the pump 120. Theoil pump 120 is similar to the oil pump 120 shown in FIGS. 12-16discussed herein. As oil flows through the main screen 816 into theannulus 818, any debris or particulate matter entrained with the oilthat has a diameter larger than the diameter of the plurality of holes816 a is prevented from flowing into the annulus 818 and thereforeretained within the cavity 817. A portion of the particulate matter maybe retained upon the inner surface of the main screen 816 as oil flowstherethrough.

As discussed above, the particulate matter that is retained upon theinner surface of the main screen 816 decreases the volume of oil thatcan flow through the main screen 816 because more and more holes 816 ain the main screen 816 become partially or totally blocked byparticulate matter retained upon the inner surface of the main screen816 with continued operation, which leaves a smaller total surface areaavailable for oil to flow through the main screen 816. As discussedabove, with continued fryer operation, the pressure at the inlet of thepump suction 122 decreases with the decline in flow through the mainscreen 816, and the oil flow rate through the pump 120 simultaneouslydecreases. As with alternative embodiments discussed herein, a controlsystem 92 (shown schematically in FIG. 20b is provided with the fryerand directs the operation of the components of the filter mechanism 810.The detailed logic steps performed by the control system 92 discussedabove is illustrative of the logic used by the control system 92discussed herein. The control system 92 may receive signals proportionalto the oil flow rate through the pump 120, the pump suction 122pressure, the passage of time, one or more oil vat temperatures, orother monitored parameters, and directs the operation of a scrapperassembly 820 disposed within the primary filter assembly 811 as well asother components of the filter mechanism 810 and the fryer, such as thepiston 840 (and chopping mechanism 900, where provided).

As best shown in FIGS. 38-39 and 48, the scraper assembly 820 ispartially mounted within the cavity 817 and includes at least oneelongate scraper 824 that includes an edge 824 a that contacts and movesalong the inner surface of the main screen 816 to mechanically agitateand remove any particulate matter stuck thereto. The scraper 824 may beconnected to a rotatable shaft 822, which when rotated causes thescraper 824 to move along the inner surface of the main screen 816. Insome embodiments, the scrapper assembly 820 may include one or morescrapers 824 that are each connected to the shaft 822 to simultaneouslymove along the main screen 816. In some embodiments, the two or morescrapers 824 may each be connected to the shaft 822 with a spring orother biasing member, which urges the scraper 824 radially outward fromthe shaft 822 to promote contact between the scraper 824 and the mainscreen 816. The shaft 822 is connected to a motor 828, and may include atransmission 826 therebetween. As shown in FIG. 38, the motor 828 andtransmission 826 are normally disposed outside of the main housing 812with the shaft 822 extending through a hole in the cover 813 of the mainhousing 812.

The motor 828 may be selectively energized by the control system 92,which allows or provides electrical current flow to the motor 828(through contacts, relays, switches, or the like) when the controlsystem 92 senses a condition of reduced oil flow to the pump suction122, a reduced pressure at the pump suction 122, a monitored number ofcycles of the fryer, a monitored elapsed time since the last operationof the scrapper assembly 820, or another useful monitored parameter. Insome embodiments, the control system 92 is configured to cause scraperassembly 820 operation when about 5 inches of vacuum is sensed at theinlet of the pump 120. In other embodiments, the control system 92 maybe configured to cause operation of the scrapper assembly 820 at othersuitable inlet pressures within the range of about 10 inches of vacuumto about 2 pounds of positive pressure, or within other ranges,depending on the desired frequency of scraper assembly 820 operation.Similarly, the control system 92 may additionally or alternatively beconfigured to cause scraper assembly 820 operation based on a manualcommand from the user. The motor 828 is energyzed by the control system92 to cause the shaft 822 to rotate a full revolution within the mainhousing 812, multiple full revolutions, or only a partial revolutionwhen two or more scrapers 824 are provided with the scraper assembly820.

As the scraper assembly 820 removes debris and particulate matter fromthe inner surface of the main screen 816, the removed material tends tofall out of the main housing 812 and travel to the lower housing 831,which is a part of the debris extraction mechanism 830. The removedmaterial often forms clumps and falls downward through the main housing812 due to its relatively large mass in comparison to the mass of theoil received from the vat 14 into the main housing 812.

The debris extraction mechanism 830 includes the lower housing 831 and asecondary screen 832 disposed coaxially within the lower housing 831.The lower housing 831 and the secondary screen 832 are dimensioned toform an annulus therebetween (similar to annulus 818 discussed above).The lower housing 831, the secondary screen 832, and an end cap cover838 disposed upon the open end of the lower housing 831 may be alignedtogether by front and rear cross bars 862, 864, which are disposed onopposite sides of the lower housing 831 and bolted or otherwise fixedtogether.

The secondary screen 832 includes a plurality of holes 832 a disposedabout the surface area thereof to allow oil to flow therethrough, butsubstantially prevent particulate matter from flowing therethrough. Thesecondary screen 832 is constructed similarly to the main screen 816discussed above. The secondary screen 832 may additionally include aninlet aperture 832 b that is disposed proximate to an inlet aperture 831a of the lower housing 831 to allow oil and particulate matter to flowfrom the cavity 817 to within the inner diameter of the secondary screen832.

An oil pipe 836 is provided between the annulus disposed between thelower housing 831 and the outer surface of the secondary screen 832 andthe cavity 817 to allow any oil flowing through the secondary screen 832to return to the cavity 817, and ultimately flow through the oil pump120. As appreciated by those of ordinary skill, there normally is littleto no oil flow through the secondary screen 832 and the oil pipe 836during normal operation because the pressure within the cavity 817 isnormally substantially the same as the pressure within the lower housing831.

An elongate cylindrical piston 840 is reciprocatingly mounted withrespect to the lower housing 831 to allow piston 840 movement between anormal position with a front face 841 of the piston 840 disposed withinthe lower housing 831 and proximate to a closed end thereof to form aleakage barrier from the lower housing 831 at the closed end 831 cthereof (FIGS. 38 and 40-42), and an extraction position (FIGS. 43-44)where the front face 841 extends out of the opposite end of the lowerhousing 831 and presses the compressing face 854 of the end cup, or endcap, 850 (FIG. 39-40, discussed below) away from the lower housing 831.The inner surface of the closed end 831 c of the lower housing 831 mayinclude one or more o-rings or similar structures disposed in seriesthat are at least partially compressed by the piston 840 tosubstantially prevent oil from leaking out of the lower housing 831therebetween. The piston 840 has an outer diameter only slightly smallerthan the inner diameter of the secondary screen 832, which causes thefront face 841 of the piston 840 to scrape the secondary screen 832 asthe piston 840 translates within the lower housing 831. As the piston840 translates from the normal position to the extraction position, anyparticulate matter disposed within the lower housing 831 is pushedthrough the lower housing 831 and toward the compressing face 854 of theend cup 850 by the front face 841 of the piston 840.

The translation of the piston 840 from the normal position to theextraction position causes the inlet apertures 831 a, 832 b of the lowerhousing 831 and secondary screen 832, respectively, to be blocked by thecylindrical body, or skirt, of the piston 840 such that oil andparticulate matter disposed within the cavity 817 is prevented fromtraveling into the lower housing and debris extraction mechanism 830.The blockage of the inlet apertures 831 a of the lower housing 831encloses the debris extraction mechanism 830 and allows for compressionof debris and particulate matter between the piston 840 and the end cup850 for ultimate removal from the extraction mechanism 830, as discussedbelow. As can be understood, as the piston 840 translates toward the endcup 850 (and the inlet aperture 831 a of the lower housing 831 becomesblocked) the oil pressure within the lower housing increases due to thedecreasing volume within the lower housing 831 between the piston 840and the end cup 850. The as the oil pressure increases, oil flow throughthe secondary screen 832 and the oil pipe 836 similarly increases due tothe differential pressure between the inner housing 831 and the cavity817.

The piston face 841 ultimately contacts a compressing face 854 of themovable end cup 850 as the piston 840 nears the extraction position. Asdiscussed below, the compressing face 854 is biased toward the pistonface 841 with one or more springs 853, which initially prevents thecompressing face 854 from translating upon contact with the piston 840.With continued motion of the piston 840 toward the extraction position,any particulate matter disposed between the compressing face 854 and thepiston 840 is compressed, causing any oil remaining with the particulatematter to flow out from between the piston face 841 and compressing face854 (due to the compression and high pressure therebetween) and anysolid particulate matter therebetween to break up and crumble under thecompressive forces. With further translation of the piston 840 towardthe extraction position, the outward force imparted upon the compressionface 854 ultimately overcomes the inward biasing force of the one ormore springs 853 causing the compressing face 854 to translate alongwith the piston 840.

The translation of the piston 840 through the lower housing 831 iscontrolled by the control system 92, which selectively translates thepiston 840 from the normal position to the extraction position, andlater returning the piston 840 to the normal position after apredetermined dwell time. The control system 92 may cause the piston 840to cycle based on at least one of a number of different operationalparameters, such as, a predetermined number of scraper assembly 820cycles, a predetermined number of cooking cycles of the fryer, andelapsed time from the previous piston 840 cycle, or the like.Additionally, the control system 92 may cause a piston cycle upon amanual command by the user.

The piston 840 is mechanically connected to an electromechanicalapparatus to automatically translate the piston 840 between the normaland extraction positions. As shown in FIGS. 39 and 44, the piston 840may be mechanically connected with a first linear actuator 880 to causelinear motion of the piston 840. The first linear actuator 880 includesa telescopic arm 880 a that is selectively advanced outward or withdrawninto the body of the device. The end of the telescopic arm 880 a ismechanically fixed to a piston follower 842 that is fixed to an end ofthe piston 840 opposite from the forward face 841. As shown in FIGS.38-39 and 40-43, the debris extraction mechanism 830 may include two ormore guide rails 844 that extend along the length of the mechanism toalign and control the movement of many of the components of themechanism 830. The piston follower 842 slides along the guide rails 844to align the piston 840 (and follower 842) upon linear motion of thetelescopic arm 880 a. As shown in the figures, the piston 840 isdisposed in the normal position when the telescopic arm 880 a isextended from the body of the linear actuator 880, and urges the piston840 toward the extraction position (i.e. into contact with thecompressing face 854 of the end cup 850) when the telescopic arm 880 ais pulled into the body. As can be understood in an alternateembodiment, the piston 840 and linear actuator 880 can be disposed inthe opposite manner, with the piston 840 moving toward the extractionposition when the telescopic arm 880 a moves away from the body of thelinear actuator 880. In other embodiments, the piston 840 may betranslated by a motor with or without a transmission disposedtherebetween, a moving or stationary electromagnet, a lead screw, orwith other structures suitable for causing controlled linear motion ofan object known in the art.

As best shown in FIGS. 40, 41, and 43, the end cup 850 is translatablymounted proximate and extending into a portion of the open end 831 d ofthe lower housing 831. The end cup 850 includes a compressing face 854that is translatably mounted within a hollow rear body 852. The body 852includes a forward sealing face that is configured to normally providesurface-to-surface contact with the sealing end 838 of the lower housing831 to prevent oil leakage from the open end 831 d of the lower housing831. The compressing face 854 includes a solid forward face portion thatnormally extends through the open end 831 d and into the lower housing831. The outer diameter of the face portion of the compressing face 854is only slightly smaller than the inner diameter of the secondary screen832 and a sealing end 838 of the lower housing 831, which additionallysubstantially prevents oil leakage from the lower housing 831 throughthe open end 831 d.

The end cup 850 is biased into a position where the compressing face 854at least partially extends within the open end 831 d of the lowerhousing 831 (and the aperture 904 a of the supporting member 904, whereprovided (FIGS. 50-52)) by a spring 868 that is disposed between thehead of an actuator pin 867 and a guide flange 866. The actuator pin 867is connected to a rear end (i.e. the end opposite from the telescopicarm 890 a) of a second linear actuator 890 (discussed below). Asdiscussed below the telescopic arm 890 a is ultimately connected withthe end cup 850 (by way of the end cup drive bar 860 and end cup cover856 in some embodiments). The guide flange 866 is fixed to the siderails 870, which are additionally fixed to the front and rear cross bars862, 864. Because the guide flange 866 is fixed with respect to siderails 870 and therefore the lower housing 831 (which are fixed by thefront and rear cross bars 862, 864), the spring 867 normally urges theactuating pin 867 away from the lower housing 831 and second linearactuator 890, which in turn urges the compressing face 854 of the endcup 850 through the open end of the lower housing 831.

The compressing face 854 includes a rear portion with a larger diameterthan a forward end of the rear body 852 (and the forward portion of thecompressing face 854), which allows the compressing face 854 to moverearwardly (i.e. when urged rearwardly by the piston 840 moving towardthe extraction position) with respect to the rear body 852, but anyrearward motion of the rear body 852 ultimately causes similar rearwardmotion of the compressing face 854. The rear portion 852 of the end cup850 is fixed to an end cup cover 856 which is fixed to an end of each ofthe plurality of guide rails 844 with bolts or other types of fasteners.In some embodiments the guide rails 844 may include threaded ends thatare received within tapped holes in the end cup cover 856, or in otherembodiments, the guide rails 844 may include taped holes that receivefasteners that extend through apertures in the end cup cover 856. One ormore springs 853 may be disposed between the end cup cover 856 and thecompressing face 854 to bias the compressing face 854 into its normalposition extending within the lower housing 831.

The compressing face 854 may include one or more pins 858 that extendfrom the opposite side of the compressing face 854 from the front sidefacing the piston 840, and additionally extend through apertures definedin the end cup cover 856. The pins 858 extending from the compressingface 854 are configured to selectively contact a corresponding number ofswitches or other signaling mechanisms 858 a when the compressing face854 is translated rearwardly after engagement with the piston face 841(and the biasing force of the spring 853 is overcome). In someembodiments, the pins 868 contact the switches 858 a when thecompressing face 854 is translated between about 1 and 1.125 inches bythe piston 840. One of skill in the art will understand that this andother dimensions are variable and dependent on the dimensions of theother components in the debris extraction mechanism 830. When the pins858 contact the switches 858 a, a second linear actuator 890 (or otherelectromechanical translation mechanism, as discussed above withreference to first linear actuator 880) is enabled, which causes atelescopic arm 890 a to translate. The telescopic arm 890 a of thesecond linear actuator 890 is mechanically fixed to the end cup cover856. The telescopic arm 890 a translates toward the end cup 850, the endcup cover 856 translates in the same direction, which pulls the rearportion 852 (fixed to the end cup cover 856) and the compressing face854 away from the front face 841 of the piston 840. The telescopic arm890 a may travel 4 inches, or other suitable travel distances based uponthe size of the other components of the embodiment.

As the end cup 850 is pulled away from the piston 840, the compressingface 854 additionally is withdrawn from within the lower housing 831(and aperture 904 a of the supporting member 904, when provided) untilcompressing face 854 is translated to a position where a gap 859 (FIGS.43-44) is formed between the compressing face 854 and the front face 841of the piston 840 outside of the lower housing 831. As the end cup 850is initially withdrawn from the piston 840 by the telescopic arm 890 a,the compressing face 854 is initially urged again toward the piston 840due to the biasing force of the spring 853. With additional movement ofthe end cup 850, the compressing face 854 is again withdrawn from thefront face 841 of the piston 840, which provides space, or a gap 859,for any particulate matter or debris previously disposed therebetween tofall through the gap 859 and out of the debris extraction mechanism 830.The piston 840 forms a seal with sealing end 838 of the lower housing831 to prevent oil leakage from the lower housing when the end cup 850is withdrawn from the lower housing 831. In some embodiments, the gap859 may be about 2.25 inches, while in other embodiments the gap 859 maybe different lengths dependent on the dimensions of the componentswithin the mechanism 830.

In some embodiments a tray, bucket, or similar structure (not shown) maybe disposed below the sealing end 838 to catch any falling debris forease of cleaning and ease of use. As discussed above, a significantportion of the oil previously disposed between the front face 841 of thepiston 840 and the compressing face 854 was urged through the secondaryscreen 832 (and ultimately to the cavity 817 via the oil pipe 836) dueto the large pressure exerted upon the oil when compressed between thecompressing face 854 and the front face 841 of the piston 840 (and thedifferential pressure between the lower housing 831 and the cavity 817).Accordingly, when the compressing face 854 is translated out of thelower housing 831 and away from the piston 840, a minimal amount of oilis lost from the filter system 810 and the fryer.

As best shown in FIGS. 39-42, the debris extraction mechanism 830 mayadditionally include an end cup drive bar 860, which is rigidlyconnected to the plurality of guide rails 844. The end cup drive bar 860may be fixed to the guide rails 844 by a crank cotter pin or by othertypes of structures and fasteners as known in the art. The end cup drivebar 860 is directly connected with the telescopic arm 890 a of thesecond linear actuator 890, such that the end cup drive bar 860 and theguide rails 844 are each translated in parallel to the telescopic arm890 a when the telescopic arm 890 a is translated by the second linearactuator 890. In some embodiments, the end cup drive bar 860 may includea protrusion 860 a that connects with the telescopic arm 890 a with apin, a fastener, or other known removable mounting structures. The endcup drive bar 860 may be provided in a substantially “U” shape, with twolegs that include mounting structures to fix the end cup drive bar 860to each of the plurality of guide rails 844, with a central section thatconnects the two legs. As shown in FIG. 42, the geometry of the end capguide rail 860 may such that the central portion is disposed below thelower housing 831 to allow the end cap guide rail 860 to translate withrespect to the lower housing 831 and to promote a compact overall designfor the debris extraction mechanism 830.

In some embodiments a chopping mechanism may be provided toreciprocatingly move between the piston face 841 and the compressingface 854 of the end cup 850 when the end cub 850 is withdrawn from thelower housing 831 to create the gap 859 therebetween. The choppingmechanism contacts (or moves closely parallel to) one or both of thefront face 841 of the piston 840 and the compressing face 854 of the endcup 850 to mechanically strip debris stuck to that structure and urgethe debris out of the debris extraction mechanism 830 due to gravity.Particulate matter or debris that is urged from the gap 859 and scrapedfrom one or both of the compressing face 854 and piston face 841 mayfall to a collection structure (not shown) disposed below the debrisextraction mechanism 830 due to gravity. In other embodiments, otherremoval structure (whether manually or automatically controlled) totransport removed particulate matter away from the extraction mechanism830 may be provided.

In other embodiments shown in FIGS. 50-52, a chopping mechanism may bemovably mounted to the debris extraction mechanism 830 to remove debrisdisposed between the front face 841 of the piston 840 and thecompressing face 854 of the end cup 850. The chopping mechanism includesa guillotine 900 that is movable between a retracted position (FIG. 50)where the guillotine 900 is disposed above the end cup 850 and to asecond, lower position (FIG. 51) where the guillotine 900 is disposedwithin the gap 859 between the piston 840 and the end cup 850. In someembodiments, as can be understood with reference to FIGS. 43, 50 and 51,as the guillotine 900 slides from the retracted position to the lowerposition, the inner surface of the guillotine makes sliding contactwith, or translates in very close proximity with, the front face 841 ofthe piston 840.

In other embodiments, the guillotine 900 may move between the retractedand lower position while making sliding contact with, or translating invery close proximity to the compressing face 854 of the end cup 850. Instill other embodiments, the guillotine 900 may make sliding contactwith or translating in very close proximity to each of the front face841 of the piston 840 and the compressing face 854 of the end cup 850.

The guillotine 900 is movably mounted to the debris extraction mechanism830 with a linkage as aided by a supporting member 904. The linkageincludes a pivotable frame 910 that is pivotably mounted to thetelescoping arm 890 a of the second linear actuator 890. Specifically,the frame 910 includes a slot 912 that receives a pin 890 b that isfixed to the telescoping arm 890 a, such that telescopic motion of thearm 890 a causes the pin 890 b to translate through the slot 912. Theslot 912 includes a horizontal first portion 912 a and an oblique secondportion 912 b that is disposed at an obtuse angle with respect to thefirst portion 912 a. The frame 910 includes an extended portion 913 thatis pivotably mounted with a pinned connection 914 a with a bracket 914that is fixed to the side rail 870 that supports the second linearactuator 890. The frame 910 receives a distal end of a member 908 thatincludes an opposite end that is fixed or connected with the guillotine900. As shown in FIGS. 50 and 51, the member 908 may include twosubstantially perpendicular portions that connect to each of the frame910 and the guillotine 900, respectively. In other embodiments, themember 908 may be of any size, shape, and orientation necessary totranslate the guillotine 900 based on motion of the second linearactuator 890 or other convenient mechanism.

The guillotine 900 is translatably mounted upon a supporting member 904that is fixed to the lower housing 831. As shown in FIG. 50, thesupporting member 904 may be fixed to the front cross bar 862, which isin-turn fixed to the lower housing 831. FIG. 52 provides a detail viewof the supporting member 904 that includes a central aperture 904 awhich provides a path for at least the compressing face 854 of the endcup 850 to extend therethrough into the lower housing 831 in a positionto selectively receive the front face 841 of the piston 840. Thesupporting member 904 further includes two oppositely extending flanges905 that rest within a portion of a track 902 defined on opposite endsof the guillotine 900. An inner surface of the guillotine 900 isslidable past an outer surface of the supporting member 904 as theguillotine 900 slides with respect to the supporting member 904.

As can be understood with comparative reference to FIGS. 50-51, as thearm 890 a of the second linear actuator 890 telescopically translatesoutward to cause the end cup 850 to translate away from the lowerhousing 831 and the piston 840, the pin 890 b slides within thehorizontal first portion 912 a of the slot 912. With sufficient motionof the leg 890 a, the pin 890 b enters the second portion 912 b of theslot 912, which causes the frame 910 to pivot about the bracket 914 withthe pinned connection 914 a due to the obtuse second portion 912 b ofthe slot 912. As the frame 910 pivots, the distal end of the member 908is moved downward, which similarly causes the guillotine 900 to slidedownward as constrained by the connection between the flanges 905disposed upon the supporting member 904 and the track 902 of theguillotine 900. The length of the first portion 912 a is such that theframe 910 does not pivot until the gap 859 is sufficient to receive theguillotine 900 therewithin.

As the guillotine 900 slides downward, the guillotine slides past thefront face 841 of the piston 840 (whether in contact with or in closeproximity, such as between about 0.01 and 0.03 inches from the frontface 841) any particulate matter or debris retained between the piston840 and the end cup 850 is urged from the respective component withinthe debris extraction mechanism 830, due to the mechanical force of theguillotine 900 and gravity. After a fixed dwell time, the second linearactuator 890 pulls the arm 890 a telescopically toward the body of thelinear actuator 890, which causes the pin 890 b to side within thesecond portion 912 b of the slot 912 toward the first portion 912 a ofthe slot 912. As the pin 890 b moves within the second portion 912 b ofthe slot 912, the frame 910 is pivoted about the bracket 914 and theguillotine 900 is urged upward along the supporting member 904 due tothe force provided thereto by the member 906 and the frame 910. Theguillotine 900 is fully withdrawn from the gap 859 when the pin 890 b isat the vertex of the first and second portions 912 a, 912 b of the slot912. With continued inward movement of the arm 890 a, the guillotine 900is fixed above the end cup 850 (because the frame 910 no longer pivotsupon the bracket 914) and the end cup 850 is urged toward its normalposition with the compressing face 854 disposed within the open end 831d of the lower housing 831 and through the supporting member 904.

In other embodiments, the chopping mechanism may be disposed and operatesimilarly to the leg 1780 and associated components thereof, which arediscussed above and shown in FIGS. 30-32 and 35-35 a.

In some embodiments shown in FIGS. 47 and 49, the control system 92 mayadditionally include a level control subsystem 1000 to control the levelor volume of oil within the vat 14 within a predetermined normaloperational range. While the level subsystem 1000 is discussed withrespect to the embodiment shown generally in FIGS. 38-52 and controlledby the control system 92, the level subsystem 1000 could equally beinstalled in the other filter embodiments discussed above and operatedby control systems 90 or 91 discussed above. The discussion of thecontrol systems 90 and 91 including the level control subsystem 1000 isnot repeated herein for the sake of brevity.

The fryer may be configured to selectively receive a flow of replacementoil from a storage volume 1001 through a pipe 1002 connectedtherebetween. The pipe 1002 may be configured to provide replacement oilfrom the storage volume 1001 directly into the vat 14, or in otherembodiments, the replacement oil may enter the fryer upstream of theheat exchanger 130 or at another convenient location to at leastpartially heat the oil prior to entering the vat 14. As shown in FIG.49, in some embodiments the storage volume 1001 may be selectivelyfluidly connected to the pump 120 so that the pump 120 provides themotive force to urge replacement oil into the system from the storagevolume 1001. In some embodiments, the pump 120 may reversible such thatthe length of piping fluidly connected to the storage volume 1001 is atthe pump suction 122, which vacuum drags oil from the storage volume1001 through the pump 120 and ultimately to the vat 14. In embodimentswhere the pump is reversible for selective addition of oil through thepump 120, one or more isolation valves 1004 (such as three way valvesshown on FIG. 49) may be provided so that the control system 92 mayautomatically reposition the appropriate valves for the correct flowpath with the fryer for the specific desired evolution. In otherembodiments shown in FIG. 47, the storage tank 1001 and vat 14 may berelatively configured to allow oil to gravity drain to the vat 14 whenthe isolation valve 1004 is opened (whether manually or automatically bythe control system).

The vat 14 may include one or more level detectors or sensors thatprovide a signal to the control system 92 proportional to the oil levelwithin the vat 14. In some embodiments, the vat 14 may include two fluidactivated switches or sensors (which may be capacitive switches,sonoswitches, or similar switches that are configured to detect thepresence or absence of fluid proximate thereto), a first sensor 1005 apositioned at a high oil level mark and a second sensor 1005 bpositioned at a low oil level. When the second sensor 1005 b no longerdetects oil proximate thereto, the control system 92 causes a remotelyoperable isolation valve 1004 disposed within the pipe 1002 to open,allowing oil flow from the storage volume 1001 to the vat 14. Thecontrol system 92 ultimately receives a signal from the first sensor1005 a that oil is proximate thereto, and the control system 92 causesthe valve 1004 to shut, stopping the flow of oil to the vat 14. In otherembodiments, the control system 92 may receive a signal only from a lowlevel sensor 1005 b, and allow oil flow to the vat 14 from the storagevolume 1001 for a predetermined period of time. The storage volume 1001and the vat 14 may be configured such that oil flows to the vat 14 dueto gravity, or in other embodiments, a pump may be provided to urge oilto the vat 14 when the isolation valve 1004 is opened by the controlsystem 92.

Turning now to FIG. 46, a plurality of fryers 800 may be disposed inparallel for simultaneous cooking with a single debris extractionmechanism 830 a fluidly connected thereto to receive particulate matterfrom each of the fryers 800. Specifically, each of the fryers 800 mayinclude a primary filter assembly 811 disposed to receive cooking fluid(referred to as oil herein, but as one of skill in the art willunderstand the cooking fluid may alternatively be water or other fluids)from a vat 14 of the fryer. The primary filter assembly 811 for eachfryer is constructed as discussed above and includes a main housing 812with coaxial main screen 816 and a scraper assembly 820. The annulus 818within the main housing 812 is fluidly connected to the suction of apump 120, which urges the oil to return to the vat 14 then to a heatexchanger 130 disposed therebetween. The scraper assembly 820 iscontrolled by a control system 92 that selectively controls the scraperassembly 820 using one or more of the parameters discussed above.

Upon operation of the scraper assembly 820, particulate matter isremoved from the inner surface of the main screen 816 and falls throughan outlet aperture of the main housing 812. The particulate matter (andoil flowing therewith) is received within a debris transport mechanism960 that is fluidly connected to the outlet of the main housing 812. Thedebris transport mechanism 960 is connected to two or more fryersmounted proximate to each other to remove particulate matter from themain housing 812 of each dedicated primary filter assembly 811.

The debris transport mechanism 960 is configured to transport thecollective volume of particulate matter received from each primaryfilter assembly 811 to a single debris extraction mechanism 830 a forultimate removal of particulate matter from the system. The debrisextraction mechanism 830 a is constructed and operates similarly to thedebris extraction mechanism 830 discussed above and shown in FIGS.38-45. Any differences between debris extraction mechanisms 830 a and830 are discussed herein.

The debris extraction mechanism 830 a receives particulate matter fromthe debris transport mechanism 960 within a lower housing 831. A piston840 is configured to selectively translate through lower housing 831 toremove collected particulate matter therefrom and ultimately contact thecompressing face 854 of an end cup 850. The piston 840 is urged withinthe lower housing 831 by a linear actuator 880 (or otherelectromechanical system) that may be automatically controlled by acontrol system 92 and/or manually controlled by the user. The controlsystem 92 may be configured to direct operation of the linear actuator880 (and therefore the piston 840 mechanically connected thereto, asdiscussed above) either due to a parameter monitored by the controlsystem 92 reaching a predetermined setpoint, a monitored number ofcycles of the scraping mechanisms 820 of each primary filter assembly811 (either a total number of cycles of all of the scraping mechanisms820, or a number of cycles of a single scraping mechanism 820), a totalnumber of cooking cycles of the collective fryers or a single fryer, oran elapsed time between a previous cycle of the piston 840 within thedebris extraction mechanism 830 a. In situations where multiple fryersare fluidly connected to a single debris extraction mechanism 830 a,and/or a single primary filter 811, each fryer may include a dedicatedcontrol system 92, with each control system 92 being capable ofoperating all associated components (i.e. the one or more primaryfilters 811 and the combined debris extraction mechanism 830 a) andprogrammed for selective control using a master/slave relationship asknown in the art.

Upon translation of the compressing face 854 by the piston 840, a linearactuator 890 (or other electromechanical mechanism) translates the endcup 850 away from the piston 840 to provide a gap 859 to allow foreignmaterial disposed between to leave the gap, as aided by a choppingmechanism in some embodiments. Similar to the debris extractionmechanism 830 discussed above, the end cup 850 and chopping mechanism(if provided) of the debris extraction mechanism 830 a are controlled bylinear actuators based upon the position of the compressing face 854 andend cup 850 and are selectively operated by the control system 92.

The lower housing 831 of the debris extraction mechanism 830 a includesa secondary screen 832 disposed coaxially therein that forms an annulustherebetween. The annulus may be fluidly connected to a cavity 817 inone or more primary filter assemblies 811 to allow oil from the debrisextraction mechanism 830 a to return to the system through an oil returnpipe 836. In some embodiments, the oil return pipe 836 may include aplurality of branches 836 a that allow oil flow to each of the primaryfilter assemblies 811 in parallel. Each branch 836 a may include anisolation valve 836 b that allows for control of which primary filterassembly is configured to receive oil flow from the debris extractionmechanism 830 a. The isolation valves 836 b may be automatically orremotely controllable valves, such as motorized valves, solenoidoperated valves and the like, to allow for automatic control of whichprimary filter assemblies 811 are fluidly aligned with the lower housing831. In some embodiments, the control system 92 may be configured toselectively operate each isolation valve 836 b to maintain a monitoredoil level in the vat 14 of each fryer in a proper band eitherindependently or in parallel with the level control subsystem 1000. Insome embodiments, the isolation valves 836 b may alternatively oradditionally manually controllable by the user.

The debris transport mechanism 960 is configured to directly receive aflow of particulate matter, debris, and oil from an outlet of the mainhousing 812 of a primary filter assembly 811 fluidly connected to thevat 14 of each fryer. The debris transport mechanism 960 eithercontinuously or selectively urges the collected particulate matter andoil received from each primary filter assembly 811 to the inlet of thelower housing 831 of the debris extraction mechanism 830. As shownschematically in FIG. 46, the debris transport mechanism 960 may be acylindrical tube 963 with an internal Archimedes type screw, or auger,964. The Archimedes screw 964 is connected to a shaft 965 that may berotated by an external motor 966, which causes similar rotation of theArchimedes screw 964.

As well known to those of skill in the art, rotation of the Archimedesscrew 964 urges or pumps particulate matter and oil in a directionthrough the tube 964 based on the orientation of the screw threads andthe rotation of the shaft 965. One of the ends of the tube 963 includesan aperture that is in fluid communication with the lower housing 831 toallow the particulate matter and oil that is pumped to the end of thetube 963 to fall into the lower housing due to gravity. In otherembodiments, the debris transport mechanism 960 may alternativelyinclude a conveyor (with or without a plurality of cups or bucketsdisposed thereon) to urge movement of particulate matter from eachprimary filter assembly toward the lower housing 831, or othermechanisms known in the art that are suitable for moving particulatematter.

The debris transport mechanism 960 may continuously operate toconstantly urge particulate matter to the debris extraction mechanism830 a, or in other embodiments, the debris transport mechanism 960 maybe operated by the control system 92 to cyclically operate based on oneor more monitored parameters or events. For example, the control system92 may be configured to operate the debris transport mechanism 960whenever one of the scraper assemblies 820 operates in one of theprimary filter assemblies 811 of the fryers that are connected to thedebris transport mechanism 960. The control system may alternatively oralso operate the debris transport mechanism 960 after a specified numberof cycles of one or more fryers 800 connected therewith, based on aelapsed time since a previous operation, or manually by the user.

In other embodiments, a plurality of fryers 800 may be fluidly connectedto a single primary filter assembly 811, which is connected to a singledebris extraction mechanism 830. The vat 14 of each fryer may include agravity drain line that is connected to a common header that is fluidlyconnected to the cavity 817 of the main housing 812. From entry into themain housing 812, the single primary filter assembly 811 and the debrisextraction mechanism 830 operate in a similar fashion to those discussedabove. The filtered oil flows through the outlet pipe 819 to the suctionof the pump 120. The pump discharge 124 includes a single header with aplurality of branches that are fluidly connected to allow oil to flow toa heat exchanger 130 disposed within each of the plurality of fryers.

Turning now to FIGS. 12-16, a pump 120 for urging oil flow through theoil circulation system 110 is provided. The pump 120 may be a positivedisplacement pump that operates with two opposing gears 123 a, 123 b inmesh within a pump housing 121 or the pump 120 may be one of othersuitable oil pumps known in the art. The pump 120 includes a suctionport 122 and a discharge port 124, and the pressure of the oil movingthrough the pump 120 from the suction to the discharge is increased dueto the energy imparted onto the oil by the pump gears 123 a, 123 b. Thepump 120 is ultimately operated due from torque provided thereto througha motor 150 and its associated motor shaft 152. The motor 150 isconnected to the pump 120 with an intermediate seal assembly 160.

The seal assembly 160 includes a seal housing 164 that rotatablysupports and encloses a portion of an intermediate shaft 170. Theintermediate shaft 170 includes a first end 171 that is mechanicallycoupled to the motor shaft 152 with a coupling 176, and a second end 172that is mechanically coupled to the pump 120. The second end 172 of theintermediate shaft 170 may be coupled to the gears 123 a, 123 b of thepump 120 with a coupling (not shown) or may be received within anaperture of one of the two gears 123 a, 123 b to transfer torquethereto. In other embodiments, the intermediate shaft 170 may bedirectly connected to the motor shaft 152 with a tongue and groove,spline, or other direct attachment structures, which allows the coupling176 to be eliminated. An external fan (not shown) may be fixed to one ofthe intermediate shaft 170 or the motor shaft 152 to provide the forcedconvection air flow over the pump and associated components.

A radial aperture 167 is defined within the seal housing 164 thatreceives a pin 167 a therein. The intermediate shaft 170 may include agroove 173 that is defined proximate to an end of the intermediate shaft170. The pin 167 a extends through the radial aperture 167 and into thegroove 173 to retain the intermediate shaft 170 aligned within the sealhousing 164.

The shaft seal ring 174 provides a physical barrier between theintermediate shaft 170 and the seal housing 164 to substantially preventoil leakage from the seal housing 164, and additionally to prevent airfrom entering the seal housing 164 from the atmosphere. The seal housing164 may be rigidly mounted to the pump housing 121 such that the shaftseal ring 174 is supported at the distal end 164 a of the seal housing164, which is removed a significant linear distance from the pumphousing 121. The distance between the shaft seal ring 174 and the pumphousing 121 allows the shaft seal ring 174 to be maintained at asignificantly lower temperature than the oil flowing through the pump120 (and accordingly the temperature of the pump housing 121). The shaftseal ring 174 may be retained within a bore (not shown) in the sealhousing 164 to provide for proper positioning of the shaft seal ring 174with respect to the seal housing 164 and the intermediate shaft 170 foreffective torque transfer between the motor shaft 152 and the pump 120.

Because the shaft seal ring 174 is disposed at a distance from the pumphousing 121, heat must be conducted through the distance between pumphousing 121 and the shaft seal ring 174 to reach the shaft seal ring 174and increase its temperature. The distance between the two membersprovides resistance to conduction heat transfer due to the thermalconductivity of the materials defining the intermediate shaft assembly160 (as well as a greater distance to reduce radiation heat transfer tothe seal ring). Further, the increased distance to the shaft seal ring174 provides greater opportunity for the heat to be transferred awayfrom the conduction flow path due to the additional cooling componentsand structures discussed below.

It has been determined experimentally, that the service life of theshaft seal ring 174 is increased if the shaft seal ring 174 is operatedat lower temperatures, specifically lower temperatures than the nominaloil temperature during fryer operation of approximately 350 degreesFahrenheit. It has further been determined empirically that steady stateoperation of the shaft seal ring 174 at a nominal temperature of 250-300degrees Fahrenheit significantly increases the useful life of the shaftseal ring 174, and therefore similarly increases the useful life of theintermediate seal assembly 160.

The intermediate seal assembly 160 may be a unified assembly that ismountable to and removable from the pump housing 120 with the use of aplurality of fasteners (not shown). The seal housing 164 may include aflange 165 with a plurality of apertures 165 a that may be abuttedagainst the pump housing 121 and receive the plurality of fastenersextending into the pump housing 121. With this structure, only simpletools such as a screwdriver or a wrench may be required to mount theintermediate seal assembly 160 to the pump housing 121. Further, withproper alignment of the apertures 165 a with similar apertures (notshown) in the pump housing 121, the intermediate seal assembly 160 iseasily aligned to operate the pump 120 with the first end 172 of theintermediate shaft engaging the gears 123 a, 123 b of the pump 120.Further, flush surface-to-surface engagement of the flange 165 with thepump housing 121 and the presence of a one or more face seals 168substantially prevents oil leakage at the junction between the pumphousing 121 and the seal housing 164.

The opposite end 171 of the intermediate shaft 170 may be rotationallyaligned with the motor shaft 152 by a coupling 176 disposed between themotor 150 and the seal housing 164. The coupling 176 may include one ormore vanes 177 that are formed to provide a flow of air over the sealhousing 164 as the coupling 176 rotates. The air flow across the sealhousing 164 removes heat from the surface of the seal housing 164, whichlimits the amount of heat ultimately transferred to the shaft seal ring174. In some embodiments, the outer surface of the seal housing 164includes a plurality of radially extending fins 164 a, which increasesthe surface area of the seal housing 164, and accordingly increases theamount of heat transferred from the seal housing 164 to the air flowingover the external surface of the seal housing 164.

A recirculation flow path 180 may additionally be provided with theintermediate seal assembly 160, as shown schematically in FIG. 13.Specifically, the seal housing 164 may include an oil entry port 163fluidly connected with an oil return groove 166. The oil return groove166 may be defined along the length of the internal bore 164 b of theseal housing 164. The groove 166 may be aligned in parallel to theintermediate shaft 170 that extends through the seal housing 164. Theoil flowing through the groove 166 contacts the rotating intermediateshaft 170, which provides lubrication to the rotating intermediate shaft170 and additionally provides cooled oil to the seal housing 164 and theintermediate shaft 170. The addition of the relatively cooled oilremoves heat from the system, which if not removed would be ultimatelytransferred to the shaft seal ring 174.

The recirculation flow path 180 extends between the discharge 124 of thepump 120 and the oil entry port 163, which provides the driving forcefor oil flow through the recirculation flow path 180. The groove 166within the seal housing 164 is ultimately fluidly connected to thesuction 122 of the pump 120, such that the differential pressure acrossthe pump 120 drives flow through the recirculation flow path 180. Therecirculation flow path 180 is formed with an extended length of tubingthat may be disposed around the motor and/or the seal housing 164 withmultiple helical rotations of tubing, or other beneficial configurationsextending into the fryer cabinet or other portions of the fryer. As oilflows through the recirculation flow path 180, heat from the oil istransferred through the tube walls to the atmosphere due to thedifferential temperature between the oil and the atmosphere. As heat istransferred from the oil to the atmosphere, the oil temperature enteringthe entry port 163 decreases, which increases the amount of heattransfer from the seal housing 164 and intermediate shaft 170 to the oilflowing through the groove 166.

The motor 150 may be controlled with a variable frequency drive, whichallows the rotational speed of the motor shaft 152 to be variably set byaltering the frequency of the current applied to the motor. As is knownin the art, a variable frequency drive operates with solid statecontrols that can adjust the frequency and voltage of current applied tothe motor from that received by the input current. In some embodiments,a more powerful motor than would be needed to drive the pump 120 andproduce the desired flow rate through the heat exchanger 130 is providedand driven at a lower than rated speed. Accordingly, the torque producedby the larger motor is sufficient to drive the pump 120 as requiredregardless of shaft speed, which allows the shaft speed to be reduced.The reduced shaft speed creates less friction at the bearings (notshown) and the shaft seal ring 174, which decreases the heat produced byfriction. The lower amount of heat produced from friction reduces theheat input to the shaft seal ring 174 and allows the shaft seal ring 174to be operated at lower temperatures for longer useful life. In otherembodiments, a constant speed motor may be used, with a reduction geartrain (not shown) disposed between the motor shaft 152 and theintermediate shaft 170 to reduce the intermediate shaft 170 speed.

In some embodiments, the variable frequency drive motor 150 is operatedby the control system 92 (FIG. 20b ), discussed above. Similarly, themotor 150 may be operated by the control systems 90 and 91 (FIGS. 20, 20a) for the other embodiments discussed above. For the sake of brevity,the operation of the motor 150 with the control system 92 will bediscussed in detail here, but the operation of control systems 90 and 91are representative. Specifically, the control system 92 obtainsoperational signals from the fryer 10 that relate to the usage of thefryer 10. In low use or idle situations, the amount of heat required tobe added to the oil by the heat exchanger 130 (or electric heaterassembly 144) to maintain the oil in the vat 14 at the nominaltemperature is reduced. Additionally, in low use or idle situations theamount of crumbs and other foreign material that is added to the oil isreduced, so the need to operate the filter 20 is reduced. Accordingly,the control system 92 receives operational parameters that relate theperformance and use of the fryer 10 and operates the pump 120 (throughmodifying the motor operation) to reduce flow through the heat exchanger130 and the filter 20 in extended low use or idle situations.

The control system 92 may receive data that is proportional to thetemperature of the oil within the vat 14 from one or more thermocouplesor other temperature monitoring instruments known in the art. Thecontrol system may also monitor data that relates to the performance ofthe filter 20, as discussed above, as the amount of foreign materialobstructing flow through the screen 40 is at least partiallyproportional to the volume and type of food product cooked by the fryer10.

If the control system 92 senses that the fryer 10 has been idling or lowuse for a predetermined delay time, the control system 92 secures thepump 120 my removing current flow to the motor 150. In other embodimentsthe control system may alternatively reduce the rotational speed of thepump motor shaft 152 by lowering the frequency of the input current tothe motor 150. The lower oil flow through the pump 120 decreases theaeration of the oil, to maximize the useful life of the oil.Additionally, the lower speed of the motor 150 decreases the powerconsumption of the motor 150, which increases the efficiency of thefryer 10. Upon oil temperatures decreasing below a predeterminedthreshold or upon the operator manipulating a specific input to thecontrol system, the control system 92 restores the normal speed of themotor shaft 152 by increasing the frequency of the input current to themotor 150, which increases pump 120 speed and flow through the heatexchanger 130 and the filter 20. In some embodiments, heavier cookingloads may trigger a higher energy input rate and commensurately higherpump 120 flow rate.

Turning now to FIGS. 1-3, a heat exchanger 130 for the fryer 10 isprovided. The heat exchanger 130 includes one or a plurality of pipes132 that receive oil flow for the discharge 124 of the pump 120 andreturn oil to the vat 14. The heat exchanger 130 may be disposed in theflue 18 of the fryer 10. In some embodiments, heated air flows past thepipes 132 in the heat exchanger 130 such that heat from the air istransferred to the oil flowing through the heat exchanger pipes 132 withconvection heat transfer. In embodiments with air flow over the heatexchanger pipes 132, the air within the fryer 10 is heated due to acombustion process with a plurality of burners 15 aligned to receiveambient air, and send the heated combustion air toward the flue 18. Insome embodiments, the burners 15 may be atmospheric style burners, andin other embodiments, the burners may be enclosed power burners (notshown). The design and operation of both atmospheric and power burnersis known in the art.

As best understood with reference to FIGS. 2 and 3, the air heated bythe burners 15 flows through a plenum 17 under the oil vat 14, whichallows some heat from the air to transfer to the vat 14 by convectionheat transfer. After passing through the plenum 17, the heated airenters the flue 18 and transfers heat to the oil flowing through theheat exchanger pipes 132. In some embodiments, the heat exchanger 130may include a plurality of parallel pipes 132 that direct oil from thepump 120 to the vat 14. The parallel pipes each receive oil flow from acommon header 134 that is fluidly connected to the pump discharge 124.The parallel pipes 132 allow for a significant amount of heat transferarea to be disposed within the heat exchanger 130, while minimizing theamount of head loss within the heat exchanger 130 due to frictionallosses between the oil and the pipe 132 walls, minimizing the size ofthe pump 120 and the power to operate the pump 150. Further, in someembodiments the pipes 132 of the heat exchanger 130 form a serpentinepattern to increase the length of the heat exchanger 130 piping disposedwithin the flue 18, which increases the amount of heat transferred tothe oil from the air due to increases surface area of the heat exchangerpiping 132. The increase in total heat transfer area allows the surfacetemperatures of the heat exchanger piping 132 to be lower than would berequired with less heat transfer area.

In some embodiments, the heat exchanger 130 is configured to maximizeheat transfer efficiency, while preventing turbulent flow conditionswithin the vat 14 as oil enters from the heat exchanger 130. Forexample, it has been experimentally determined that flow rates of about4.5 to 5.0 g.p.m. of oil entering the vat 14 from the heat exchangeroften yield unsatisfactory turbulent oil flows 14 within a normal 14×14inch vat 14 found on many conventional fryers. While it isdisadvantageous to provide inlet oil flows at or above about 4.5 g.p.m.,some continuous oil flow through the vat 14 is beneficial for increasedcooking efficiency as the food product is continuously presented withrelatively hot cooking oil, which pushes away the cooler cooking oilthat has already lost heat to the food product. While the flow rateshould be below 4.5 g.p.m., the flow should rate should be high enoughto allow for sufficient flow rate through the relatively long heatexchanger 130 for sufficient oil flow through the filter (discussedabove), as well as for controlled and precise heating of the oil flowingtherethrough and for sufficient oil filtering.

In a preferred embodiment, the heat exchanger 130 is configured withfour parallel legs, which combine for approximately 19 feet of lengthand approximately 1100 square inches of heat transfer area. When thepump 120 operates at a total flow rate of about 4.25 g.p.m. through theheat exchanger 130 (and therefore the continuous filter), the oiltravels through the heat exchanger 130 for about 5 seconds, which allowsfor the oil to be heated to about 350 degrees with heat exchanger 130tube wall temperatures of between about 385-400 degrees Fahrenheit. Asmay be appreciated by those of ordinary skill in the art, changes insizes and geometry of the vat 14 and heat exchanger 130 may necessitatesimilar changes to the operation of the pump 120 and other components ofthe system. By way of example, typical donut fryers include relativelylarge oil vats, often about 24×24 inches. Because of the larger oilvolume included in this larger vat, higher pump speeds, potentiallyaround 8 g.p.m. should be used to provide for efficient heat transfer,sufficient, but not turbulent, oil flow within the vat, among otherdesign parameters.

In some embodiments, the heat exchanger 130 piping may have a pluralityof fins 133 (shown schematically in FIG. 3) to increase the effectivesurface area for heat transfer from the combustion gasses flowing pastthe heat exchanger 130 piping.

The heated air flows through the flue 18 in an upward direction W, whilethe oil flows through the serpentine pattern of the heat exchanger 130in the opposite generally downward direction X. This “cross flow”orientation maximizes the efficiency of the heat flow from the heatedair to the oil, because the differential temperature between the air andthe oil is maximized along the length of the flue 18. In otherembodiments, a plurality of electric heaters 144 a may be providedwithin a housing or plenum 144 disposed downstream of and in fluidcommunication with the oil pump 120 through which the oil flows. Theelectric heaters 144 a may be electric resistance elements as known onthe art and are continuously or cyclically operated to provide heat tothe oil flowing through the internal volume 146 of the plenum 144 tomaintain the oil in the vat at nominal operation temperatures.

A common discharge header 136 is connected to each of the parallel pipesof the heat exchanger 130 and allows for oil flow to a ring 140. Thering 140 includes a plurality of apertures 142 that allow oil to exitthe ring 140. The plurality of apertures 142 may be arranged to providea sweeping action across the bottom of the vat to assist in directingcrumbs into the filter 20, as well as providing convection currents toimprove heat transfer to the cooking food. In some embodiments, the ring140 is disposed within the vat 14 such that oil flowing from the ring140 immediately enters the vat 14. The ring 140 may be disposed belowthe top surface of oil during use to minimize the aeration of the oil asit enters the vat 14. In other embodiments, the ring 140 may be disposedoutside and surrounding the perimeter of the vat 14, and a plurality ofapertures are defined on the peripheral surfaces of the vat 14 to allowoil leaving the ring 140 to ultimately enter the vat 14. The design withthe ring 140 disposed outside and surrounding the vat 14 provides lesscrevices and low flow areas within the vat, which can be difficult toclean.

Turning now to FIG. 2a , a fryer with a continuous electric heatingsystem to heat oil received from the discharge 124 of the pump 120 maybe provided. The system includes a heater assembly 144 that receives oilat an inlet and includes one or more electric heaters 144 a disposedwithin the heater assembly 144 that provide heat to the oil flowingtherethrough within the internal volume 146 of the heater assembly 144.The output of the heater assembly is fluidly connected to the vat 14with a conduit 145 disposed therebetween. In some embodiments, theheater assembly 144 may include three electric heaters 144 a, eachpowered by one of the three different phases of a typical three phasecurrent source. In other embodiments, the heater assembly 144 mayinclude one or more heaters 144 a that are each powered from a singlephase of current, or alternatively two of the three phases of current.

In still other embodiments, two heaters 144 a may be disposed within theheater assembly 144 and receive current from two of the three typicalphases of AC current (either delta or wye connected), while the heaterassembly 144 itself acts as an electric heater and receives current fromthe remaining phase of current. This embodiment increases the surfacearea of the electric heaters 144 a available to heat the oil flowingthrough the heater assembly 144.

While the preferred embodiments have been described, it should beunderstood that the disclosure is not so limited and modifications maybe made without departing from the scope of the disclosure. The scope ofthe invention is defined by the appended claims, and all devices thatcome within the meaning of the claims, either literally or byequivalence, are intended to be embraced therein.

The invention claimed is:
 1. A method of removing particulate matterfrom liquid in a cooking appliance, comprising the steps of: receivingliquid with particulate matter from a retention volume within thecooking appliance; filtering the liquid with a cylindrical screendisposed within a primary filter; automatically scraping particulatematter from an inner surface of the cylindrical screen; receivingscraped particulate matter within a debris extraction mechanism;compressing the particulate matter within the debris extractionmechanism; and automatically removing the particulate matter from thedebris extraction mechanism.
 2. The method of claim 1, furthercomprising the step of pumping filtered liquid passing through thecylindrical screen through a heat exchanger and then to the retentionvolume.
 3. The method of claim 1, further comprising the step ofmechanically agitating the debris compressed within the debrisextraction mechanism to urge the debris to be removed from the debrisextraction mechanism.